Oxide sintered body and production method therefor, target, and transparent conductive film and transparent conductive substrate obtained by using the same

ABSTRACT

A target for sputtering or a tablet for ion plating, which enables to attain high rate film-formation and a nodule-less, an oxide sintered body suitable for obtaining the same and a production method therefor, and a transparent conductive film having low absorption of blue light and low specific resistance, obtained by using the same. It is provided by an oxide sintered body having indium and gallium as an oxide, characterized in that an In 2 O 3  phase with a bixbyite-type structure forms a major crystal phase, and a GalnO 3  phase of a β-Ga 2 O 3 -type structure, or GalnO 3  phase and a (Ga, In) 2 O 3  phase is finely dispersed therein, as a crystal grain having an average particle diameter of equal to or smaller than 5 μm, and a content of gallium is equal to or higher than 10% by atom and below 35% by atom as atom number ratio of Ga/(In+Ga) or the like.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an oxide sintered body and a productionmethod therefor, a target, and a transparent conductive film and atransparent conductive substrate obtained by using the same, and in moredetail, the present invention relates to a target for sputtering or atablet for ion plating, which enables to attain high rate film-formationand a nodule-less, an oxide sintered body suitable for obtaining thesame and a production method therefor, and a transparent conductive filmhaving low absorption of blue light and low specific resistance,obtained by using the same.

2. Description of the Prior Art

A transparent conductive film has high conductivity and hightransmittance in a visible light region, therefore, has been utilized inan electrode or the like, for a solar cell or a liquid crystal displayelement, and other various light receiving elements, as well as a heatray reflection film for an automotive window or construction use, anantistatic film, and a transparent heat generator for variousanti-fogging for a refrigerator showcase and the like.

As a well known practical transparent conductive film, there has beenincluded a thin film of tin oxide (SnO₂)-type, zinc oxide (ZnO)-type,indium oxide (In₂O₃)-type. As the tin oxide-type, one containingantimony as a dopant (ATO), or one containing fluorine as a dopant (FTO)has been utilized, and as the zinc oxide-type, one containing aluminumas a dopant (AZO), or one containing gallium as a dopant (GZO) has beenutilized. However, the transparent conductive film most widely usedindustrially is the indium oxide-type. Among them, indium oxidecontaining tin as a dopant is called an ITO (Indium-Tin-Oxide) film, andhas been utilized widely, because, in particular, a film with lowresistance can be obtained easily.

The transparent conductive film with low resistance is suitably usedwidely in a surface element or a touch panel or the like, such as for asolar cell, a liquid crystal, an organic electroluminescence and aninorganic electroluminescence. As a production method for thesetransparent conductive films, a sputtering method or an ion platingmethod has been used often. In particular, a sputtering method is aneffective method in film-formation of a material with low vaporpressure, or when control of precise film thickness is required, andbecause of very simple and easy operation thereof, it has been widelyused industrially.

In a sputtering method, a target for sputtering is used as a rawmaterial of a thin film. The target is a solid containing a metalelement constituting the thin film to be formed, and a sintered bodysuch as a metal, a metal oxide, a metal nitride, a metal carbide, or, incertain cases, a single crystal is used. In this method, in general,after making high vacuum once with a vacuuming apparatus, rare gas suchas argon is introduced, and under a gas pressure of equal to or lowerthan about 10 Pa, a substrate is set as an anode and a target is set asa cathode to generate glow discharge between them and generate argonplasma, and argon cations in the plasma are collided with the target ofthe cathode, and particles of the target component flicked thereby aredeposited on the substrate to form a film.

A sputtering method is classified by a generation method of argonplasma, and a method using high frequency plasma is called a highfrequency sputtering method, and a method using direct-current plasma iscalled a direct-current sputtering method.

In general, a direct-current sputtering method has been utilizedindustrially in a wide range, because it provides higher film-formationrate and lower cost of power source facility and simpler film-formationoperation, as compared with the high frequency sputtering method.However, the direct-current sputtering method has a disadvantage ofrequiring use of a conductive target, as compared with the highfrequency sputtering method, which can provide film-formation even byusing an insulating target.

Film-formation rate of a sputtering has close relation to chemical bondof a target substance. Because a sputtering is a phenomenon that argoncations having a kinetic energy are collided to the target surface, anda substance of a target surface is flicked by receiving energy, theweaker inter-ionic bond or inter-atomic bond of the target substanceincreases the more probability of jumping out by sputtering.

In film-formation of a transparent conductive film of an oxide such asITO by using a sputtering method, there are a method for film-formationof an oxide film by a reactive sputtering method in mixed gas of argonand oxygen, by using an alloy target (an In—Sn alloy in the case of theITO film) of metals constituting the film, and a method forfilm-formation of an oxide film by a reactive sputtering method forperforming a sputtering in mixed gas of argon and oxygen, by using anoxide sintered body target (an In—Sn—O sintered body in the case of theITO film) of elements constituting the film.

Among these, in a method for using the alloy target, relatively highamount of oxygen gas is supplied during sputtering, however, becausedependence of film-formation rate or film characteristics (specificresistance, transmittance) on amount of oxygen gas to be introducedduring film-formation is extremely high, it is difficult to producestably a transparent conductive film having a constant film thickness orcharacteristics.

In a method for using the oxide target, a part of oxygen to be suppliedto a film is supplied from the target by sputtering, and residualdeficient oxygen amount is supplied as oxygen gas. Therefore, dependenceof film-formation rate or film characteristics (specific resistance,transmittance) on amount of oxygen gas to be introduced duringfilm-formation is lower as compared with the case where the alloy targetis used, and a transparent conductive film having a constant filmthickness or characteristics can be produced more stably, and for thisreason, a method for using the oxide target has been adoptedindustrially.

Under such background, in the case where mass production offilm-formation of a transparent conductive film is performed by asputtering method, a direct-current sputtering method used an oxidetarget is adopted in most cases. In consideration of productivity orproduction cost here, characteristics of the oxide target indirect-current sputtering becomes important. That is, the oxide targetproviding higher film-formation rate under the same charging power isuseful. Further, because charging of the higher direct-current powerincreases film-formation rate the more, such an oxide target becomesuseful industrially that is capable of providing film-formation stably,without generation of target crack or abnormal discharge such as arcingcaused by nodule generation, even when high direct-current power ischarged.

The nodule here indicates a black precipitate (a protrusion substance)generating at an erosion part of the target surface, excluding only atrace part at the deepest part of the erosion, when the target is beingsputtered. In general, the nodule is said not to be a deposition of aforeign flying substance or a reaction product at the surface but adigging-residue left by sputtering. The nodule causes abnormal dischargesuch as arcing, therefore by reduction of the nodule, arcing issuppressed (refer to Non-Patent Document 1). Therefore, an oxide targetwhich does not generate the nodule, that is, digging-residue left bysputtering, is suitable.

On the other hand, an ion plating method is a method where a metal or ametal oxide is evaporated by a resistance heating or electron beamheating, and further the evaporated substance is deposited onto asubstrate after activation with plasma along with reactive gas (oxygen).Also as for a target for ion plating (which may be called a tablet or apellet) to be used for formation of a transparent conductive film,similarly to a sputtering target, use of an oxide tablet is capable ofproducing more stably a transparent conductive film having constant filmthickness and constant characteristics. The oxide tablet is required toevaporate uniformly, and it is preferable that a substance having stablechemical bond and difficult to be evaporated is not present togetherwith a substance which is present as a main phase and easily evaporated.

As described hitherto, although ITO, which is formed by a direct-currentsputtering method or an ion plating method, has been used industriallyin a wide range, in a LED (Light Emitting Diode) or an organic EL(Electro Luminescence) whose progress has been significant in recentyears, the cases have been emerged where characteristics not obtained byITO is required. As one example, in a blue LED, it has been required atransparent conductive film with high transmittance of blue light of awavelength of around 400 nm, to enhance light extraction efficiency.Light absorption of ITO in a visible region tends to increase more inthe shorter wavelength region, in the order of red light, green lightand blue light. Therefore, use of ITO as a transparent electrode of theblue LED results in loss by light absorption.

In order to avoid such a problem, in recent years, as an electrode ofvarious light emission devices, there has been proposed a transparentconductive film composed of an oxide film containing indium and gallium,as an ITO-alternative transparent conductive film having low absorptionof visible light, in particular, blue light. However, because ofinsufficient development of an oxide sintered body to be used as atarget or a tablet, mass production of transparent conductive filmhaving a good quality is not possible and thus practical applicationshave not yet been attained until now.

As for the transparent conductive film with low absorption of bluelight, there has been proposed a transparent conductive materialcontaining a gallium-indium oxide (GaInO₃) doped with small quantity ofdifferent-valent dopant such as a tetra-valent atom (for example, referto Patent Document 1). In this Document, there has been described that acrystal film of said oxide exhibits excellent transparency and a lowrefractive index of about 1.6, which improves refractive index matchingwith a glass substrate, as well as enables to attain electricconductivity in the same degree as that of a wide forbidden bandsemiconductor to be used presently. And, there have been described thatin a green or blue region, this film exhibits transmittance superior toan indium-tin oxide, and uniform and slight absorption over a visiblespectra, and also a pellet of a raw material to be used infilm-formation of said oxide, is a material with a single phase having aGaInO₃-type structure such as one represented as GaIn_(1−x)M_(x)O₃.

However, in the case where the material with a single phase having theGaInO₃-type structure is used as a target for a sputtering or a pelletfor vapor deposition, sputtering yield is low and film-formation ratedecreases extremely to about ½ of ITO, because said material with asingle phase has a stable chemical bond, which is specific to acomposite oxide, and thus it is disadvantageous industrially. Inaddition, there has been no study on a composition, a constitution orthe like of an oxide sintered body, which makes possible suppression ofnodule generation, which causes the above arcing, when condition toincrease film-formation rate by increase in sputtering voltage or thelike, is selected to overcome low sputtering yield. That is, as for theoxide sintered body as a raw material of the above transparentconductive film, there has been no consideration as far as anindustrially practical aspect.

In addition, as a transparent conductive film and an oxide sintered bodyof the same oxide type as in the above Patent Document 1, there has beenproposed a transparent conductive film having far higher conductivitythan that of GaInO₃ or In₂O₃, that is, lower specific resistance andexcellent optical characteristics, in a composition range different fromconventionally known GaInO₃, and containing Ga content of from 15 to 49%by atom represented by Ga/(Ga+In), in a pseudo two-dimensional systemrepresented by Ga₂O₃—In₂O₃ (for example, refer to Patent Document 2).

However, there is not so much detailed description on preparationcondition of the oxide sintered body of a raw material for obtaining ofthe above transparent conductive film, and as for the constitution ofthe transparent conductive film, it is shown as an amorphous state or amicrocrystalline state composed of a mixed phase such as GaInO₃, GaInO₃and In₂O₃, GaInO₃ and Ga₂O₃, however, there is no description on theoxide sintered body of a raw material. Therefore, similarly as describedabove, as for the constitution of the oxide sintered body of a rawmaterial, there has not been found any approach on an optimal state froman industrial or practical point of view, such as film-formation rate orsuppression of a nodule.

Further, as a transparent conductive film of the same oxide type as inthe above Patent Document 1, there has been proposed a transparentconductive film characterized by being composed of In₂O₃ with a Gacontent of from 1 to 10% by atom (which may be referred to as an IGOfilm), and having lower specific resistance and higher transmittance ascompared with a conventional ITO film (a transparent conductive filmcomposed of In₂O₃ added with Sn), which is formed by a film-formationmethod such as a sputtering method, as a transparent conductive filmwhich enables to correspond to, in particular, a large sized, colorizedand highly accurate liquid crystal display (LCD) (for example, refer toPatent Document 3). There has been described that the IGO film havingthe above constitution has lower specific resistance, such as a specificresistance of equal to or lower than 1×10⁻³ Ω·cm, even for a film formedat 100° C., as well as higher transmittance such as equal to or higherthan 85% in a visible region, as compared with a conventional ITO film,therefore, it can be suitably used, in particular, as a transparentelectrode of the LCD, and thus can attain high functionality and qualityenhancement such as large sized, colorized and highly accurate tendencyof LCD in the future. However, as a target to obtain the abovetransparent conductive film, there has been proposed only a compositetarget arranged with a Ga chip on an In₂O₃ target, or an In₂O₃ targetcontaining predetermined quantity of Ga, and there has been no study ona constitution or the like of the oxide sintered body, thus it is not aapproach on an optimal state from an industrial or practical point ofview, such as film-formation rate or suppression of a nodule.

Under such circumstances, the present applicant has proposed atransparent conductive film of the same oxide type as in the abovePatent Document, a sintered body target for production of a transparentconductive film, a transparent conductive substrate and a display deviceusing the same (for example, refer to Patent Document 4). In thisDocument, there has been described, as for a structure of the oxidesintered body, that it is composed of Ga, In and O, and contains theabove Ga from 35% by atom to 45% by atom, relative to total metal atoms,mainly composed of a GaInO₃ phase with a β-Ga₂O₃-type structure and anIn₂O₃ phase with a bixbyite-type structure, and X-ray diffraction peakintensity ratio to a β-GaInO₃ phase (111) of an In₂O₃ phase (400) isfrom 50% to 110%, and density is equal to or higher than 5.8 g/cm³. Inaddition, as for conductivity of the oxide sintered body, specificresistance is equal to or lower than 4.0×10⁻²Ω·cm, and in the case whereit is over this level, film-formation rate decreases and productivitydecreases, even when DC magnetron sputtering is possible.

In addition, as for a composition and a constitution structure of theabove oxide sintered body, it is only considered influence on specificresistance or light transmittance of a transparent conductive filmformed from this as a raw material, and the Ga content of below 35% byatom results in decrease in light transmittance in a shorter wavelengthregion of visible light, and the Ga content of over 45% by atomdecreases conductivity. The specific resistance is required to be from2×10⁻³Ω·cm to 8.0×10⁻³Ω·cm, and although a region of the value below1.2×10⁻³ Ω·cm is preferable, it requires for the composition of saidtransparent conductive film to have the Ga content of below 35% by atom.Accordingly, the optimal composition was selected in view ofconductivity and optical characteristics of the obtained film, and therehas not been studied on influence or the like of a composition and aconstitution of the oxide sintered body on nodule generation, as a studyitem.

Under such circumstances, appearance of an oxide sintered body havingindium and gallium has been desired, which has solved a practicalproblem such as high film-formation rate or nodule suppression that isimportant in mass production of a transparent conductive film containingindium and gallium, having low absorption of blue light and lowresistance.

-   [Patent Document 1] JP-A-7-182924-   [Patent Document 2] JP-A-9-259640-   [Patent Document 3] JP-A-9-50711-   [Patent Document 4] JP-A-2005-347215-   [Non-Patent Document 1] “Technology of a transparent conductive film    (the second Revised version)”, Ohmsha, Ltd., published on Dec. 20,    2006, p. 238 to 239

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a target forsputtering or a tablet for ion plating, which enables to attain highrate film-formation and a nodule-less, an oxide sintered body suitablefor obtaining the same and a production method therefor, and atransparent conductive film having low absorption of blue light and lowspecific resistance obtained by using the same.

The present inventors have studied in detail on influence of theconstitution phase and the constitution of an oxide sintered bodycomposed of an oxide containing indium and gallium, on productioncondition such as film-formation rate of an oxide transparent conductivefilm, by a sputtering method with a target for sputtering or by an ionplating method with a tablet for ion plating, which uses said oxidesintered body as a raw material, along with on generation of a nodulecausing arcing. As a result, the present inventors have found that inthe oxide sintered body containing indium and gallium, when it satisfiesthat (1) it is constituted by substantially an In₂O₃ phase with abixbyite-type structure having a solid solution of gallium, and a GaInO₃phase of a β-Ga₂O₃-type structure constituted by indium and gallium, oran In₂O₃ phase with a bixbyite-type structure having a solid solution ofgallium, and a GaInO₃ phase of a β-Ga₂O₃-type structure constituted byindium and gallium, and a (Ga, In)₂O₃ phase, and adjusting averageparticle diameter of a crystal grain composed of the GaInO₃ phase or theGaInO₃ phase and the (Ga, In)₂O₃ phase to equal to or smaller than 5 μm,and (2) a content of gallium in the oxide sintered body is adjusted tobe equal to or higher than 10% by atom and below 35% by atom as atomnumber ratio of Ga/(In+Ga), a transparent conductive film having lowabsorption of blue light and low specific resistance, which makespossible suppression of nodule generation, which causes the abovearcing, can be obtained, even when charge power is increased information of a transparent conductive film onto a substrate, forenhancement of film-formation rate, as well as when it satisfies that(3) the content of gallium is from 2 to 30% by atom as atom number ratioof Ga/(In+Ga+Sn+Ge), and the content of one or more kinds selected fromtin or germanium is from 1 to 11% by atom as atom number ratio of(Sn+Ge)/(In+Ga+Sn+Ge), a transparent conductive film having lowabsorption of blue light and low specific resistance, which similarlymakes possible suppression of nodule generation, which causes the abovearcing, can be obtained, and have thus completed the present invention.

That is, according to a first aspect of the present invention, there isprovided an oxide sintered body having indium and gallium as an oxide,characterized in that an In₂O₃ phase with a bixbyite-type structure is amajor crystal phase, and a GaInO₃ phase of a β-Ga₂O₃-type structure, ora GaInO₃ phase and a (Ga, In)₂O₃ phase is finely dispersed therein as acrystal grain having an average particle diameter of equal to or smallerthan 5 μm, and a content of gallium is equal to or higher than 10% byatom and below 35% by atom as atom number ratio of Ga/(In+Ga).

In addition, according to a second aspect of the present invention,there is provided the oxide sintered body in the first aspect,characterized in that the content of gallium is from 10 to 25% by atomas atom number ratio of Ga/(In+Ga).

In addition, according to a third aspect of the present invention, thereis provided the oxide sintered body in the first or the second aspect,characterized in that intensity ratio of X-ray diffraction peaks definedby the following expression, is from 8% to 58%:I[GaInO₃ phase(111)]/{I[In₂O₃ phase(400)]+I[GaInO₃ phase(111)]}×100[%](wherein I[In₂O₃ phase (400)] represents (400) peak intensity of theIn₂O₃ phase with a bixbyite-type structure, and I[GaInO₃ phase (111)]represents (111) peak intensity of a composite oxide of β-GaInO₃ phasewith a β-Ga₂O₃-type structure).

On the other hand, according to a fourth aspect of the presentinvention, there is provided an oxide sintered body having indium andgallium as an oxide, characterized in that an In₂O₃ phase with abixbyite-type structure is a major crystal phase, and a GaInO₃ phase ofa β-Ga₂O₃-type structure, or a GaInO₃ phase and a (Ga, In)₂O₃ phase isfinely dispersed therein, as a crystal grain having an average particlediameter of equal to or smaller than 5 μm, and other than indium andgallium, further one or more kinds of additive components selected fromtin or germanium are contained, and the content of gallium is from 2 to30% by atom as atom number ratio of Ga/(In+Ga+Sn+Ge), and the content ofthe additive components is from 1 to 11% by atom as atom number ratio of(Sn+Ge)/(In+Ga+Sn+Ge).

Still more, according to a fifth aspect of the present invention, thereis provided the oxide sintered body in the fourth aspect, characterizedin that the content of gallium is from 2 to 20% by atom as atom numberratio of Ga/(In+Ga+Sn+Ge), and the content of one or more kinds selectedfrom tin or germanium is from 2 to 10% by atom as atom number ratio of(Sn+Ge)/(In+Ga+Sn+Ge).

In addition, according to a sixth aspect of the present invention, thereis provided the oxide sintered body in the fourth or fifth aspect,characterized in that intensity ratio of X-ray diffraction peaks,defined by the following expression, is from 4% to 84%.I[GaInO₃ phase(−111)]/{I[In₂O₃ phase(400)]+I[GaInO₃ phase(−111)]}×100[%](wherein I[In₂O₃ phase(400)] represents (400) peak intensity of theIn₂O₃ phase with a bixbyite-type structure, and I[GaInO₃ phase(−111)]represents (−111) peak intensity of a composite oxide of β-GaInO₃ phasewith a β-Ga₂O₃-type structure).

In addition, according to a seventh aspect of the present invention,there is provided a production method for the oxide sintered body in anyof the first to the sixth aspects, by mixing the raw material powdershaving indium oxide powders and gallium oxide powders, or by adding thetin oxide powders and/or germanium oxide powders into this raw materialpowders, and mixing the mixture, and then by compacting the mixedpowders and sintering the compact by a normal pressure firing method, orby compacting and sintering the mixed powders by a hot press method,characterized by obtaining the oxide sintered body, where an In₂O₃ phasewith a bixbyite-type structure is a major crystal phase, and a GaInO₃phase, or a GaInO₃ phase and a (Ga, In)₂O₃ phase is finely dispersedtherein, as a crystal grain having an average particle diameter of equalto or smaller than 5 μm, by adjusting the average particle diameter ofthe raw material powders to equal to or smaller than 1 μm.

In addition, according to an eighth aspect of the present invention,there is provided the production method for the oxide sintered body inthe seventh aspect, characterized in that the compact is sintered at1250 to 1450° C. for 10 to 30 hours in atmosphere of oxygen presence, byadoption of the normal pressure firing method.

In addition, according to a ninth aspect of the present invention, thereis provided the production method for the oxide sintered body in theseventh aspect, characterized in that the compact is sintered at 1000 to1200° C. for 10 to 30 hours in atmosphere of oxygen presence, byadoption of the normal pressure firing method.

In addition, according to a tenth aspect of the present invention, thereis provided the production method for the oxide sintered body in theseventh aspect, characterized in that the mixed powders are compactedand sintered at 700 to 950° C. for 1 to 10 hours under a pressure of2.45 to 29.40 MPa in inert gas atmosphere or in vacuum, by adoption of ahot press method.

On the other hand, according to a eleventh aspect of the presentinvention, there is provided a target obtained by processing the oxidesintered body in any one of the first to the sixth aspects.

In addition, according to a twelfth aspect of the present invention,there is provided a target, characterized by obtaining by processing theoxide sintered body produced by the method in the eighth or the tenthaspect, wherein density of the oxide sintered body is equal to or higherthan 6.3 g/cm³, and being used in formation of a transparent conductivefilm by a sputtering method.

In addition, according to a thirteenth aspect of the present invention,there is provided a target, characterized by obtaining by processing theoxide sintered body produced by the method in the ninth aspect, whereindensity of the oxide sintered body is from 3.4 to 5.5 g/cm³, and beingused in formation of a transparent conductive film by an ion platingmethod.

On the other hand, according to a fourteenth aspect of the presentinvention, there is provided an amorphous transparent conductive filmobtained by using the target in any one of the eleventh to thethirteenth aspects, and by forming on a substrate, by a sputteringmethod or an ion plating method.

In addition, according to a fifteenth aspect of the present invention,there is provided the transparent conductive film in the fourteenthaspect, characterized in that the content of gallium in the film isequal to or higher than 10% by atom and below 35% by atom as atom numberratio of Ga/(In+Ga).

In addition, according to a sixteenth aspect of the present invention,there is provided the transparent conductive film in the fourteenthaspect, characterized in that the content of gallium in the film is from2 to 30% by atom as atom number ratio of Ga/(In+Ga+Sn+Ge), and thecontent of one or more kinds selected from tin or germanium is from 1 to11% by atom as atom number ratio of (Sn+Ge)/(In+Ga+Sn+Ge).

In addition, according to a seventeenth aspect of the present invention,there is provided the transparent conductive film in the fourteenthaspects, characterized in that the sputtering is performed undercondition that arcing does not generate, even by charging adirect-current power density of 1.10 to 3.29 W/cm².

In addition, according to an eighteenth aspect of the present invention,there is provided the transparent conductive film in any one of thefourteenth to the fifteenth to seventeenth aspects, characterized inthat arithmetic average height Ra is equal to or lower than 1.0 nm.

In addition, according to a nineteenth aspect of the present invention,there is provided the transparent conductive film in any one of thefourteenth to the eighteenth aspects, characterized in that extinctioncoefficient at a wavelength of 400 nm is equal to or smaller than 0.04.

In addition, according to a twentieth aspect of the present invention,there is provided the transparent conductive film in any one of thefourteenth to the nineteenth aspects, characterized in that specificresistance is equal to or lower than 2×10⁻³Ω·cm.

On the other hand, according to a twenty-first aspect of the presentinvention, there is provided a transparent conductive substratecomprising by forming the transparent conductive film in any one of thefourteenth to the twentieth aspects, onto one surface or both surfacesof the transparent conductive substrate.

In addition, according to a twenty-second aspect of the presentinvention, there is provided the transparent conductive substrate in thetwenty-first aspect, characterized in that a transparent substrate isany of a glass plate, a quartz plate, a resin plate or a resin film.

In addition, according to a twenty-third aspect of the presentinvention, there is provided the transparent conductive substrate in thetwenty-second aspect, characterized in that the resin plate or the resinfilm is a single body made of polyethylene terephthalate,polyethersulfone, polyarylate or polycarbonate as a material, or alaminated structure body where surface thereof is covered with anacryl-based organic substance.

In addition, according to a twenty-fourth aspect of the presentinvention, there is provided The transparent conductive substrate in thetwenty-second or twenty-third aspect, characterized in that the resinplate or the resin film is covered with a gas barrier film at onesurface or both surfaces thereof, or is a laminated body inserted with agas barrier film at the intermediate part thereof.

Further, according to a twenty-fifth aspect of the present invention,there is provided the transparent conductive substrate in thetwenty-fourth aspect, characterized in that the above gas barrier filmis one or more kinds selected from a silicon oxide film, a siliconoxynitride film, a magnesium aluminate film, a tin oxide-based film, ora diamond-like carbon film.

The oxide sintered body composed of indium and gallium of the presentinvention, when it satisfies that an In₂O₃ phase with a bixbyite-typestructure is a major crystal phase, and a GaInO₃ phase of a β-Ga₂O₃-typestructure, or GaInO₃ phase and a (Ga, In)₂O₃ phase is finely dispersedtherein as a crystal grain having an average particle diameter of equalto or smaller than 5 μm, and a content of gallium in the oxide sinteredbody is equal to or higher than 10% by atom and below 35% by atom asatom number ratio of Ga/(In+Ga), or the content of gallium is from 2 to30% by atom as atom number ratio of Ga/(In+Ga+Sn+Ge), and the content ofone or more kinds selected from tin or germanium is from 1 to 11% byatom as atom number ratio of (Sn+Ge)/(In+Ga+Sn+Ge), can suppress nodulegeneration, which causes arcing, even when film-formation rate isincreased in obtaining an oxide transparent conductive film by asputtering method or an ion plating method, and as a result, can obtaina transparent conductive film containing indium and gallium, having lowabsorption of blue light and low specific resistance, therefore, it isextremely useful industrially.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a SEM image of the oxide sintered body of the presentinvention, observed with a scanning electron microscope (SEM).

FIG. 2 is a chart showing X-ray diffraction results of the oxidesintered body of the present invention.

FIG. 3 is a graph showing relationship between charged direct-currentpower and arcing generation times, in sputtering with a target processedby an oxide sintered body.

DETAILED DESCRIPTION OF THE INVENTION

Explanation will be given below in detail on an oxide sintered body anda production method thereof, a target and a transparent conductive filmobtained by using the same, and a transparent conductive substrate ofthe present invention.

1. An Oxide Sintered Body

Up to now, there has been proposed a target for sputtering or a tabletfor ion plating of a transparent conductive film composed of an oxidecontaining indium and gallium, however, as for an oxide sintered body asa raw material thereof, there has not been studied sufficiently onoptimization of production condition for obtaining an oxide transparentconductive film by a sputtering method or an ion plating method, and theconstitution phase and the constitution of the oxide sintered body. Inthe present invention, there has been clarified influence of theconstitution phase and the constitution of an oxide sintered body, onfilm-formation rate and generation of a nodule causing arcing.

In the present invention, there are two kinds in the oxide sintered bodycontaining indium and gallium as oxides: one having a specific phasestructure, where a content of gallium is equal to or higher than 10% byatom and below 35% by atom as atom number ratio of Ga/(In+Ga)(hereafter, this is referred to as a first oxide sintered body), and onewhere, other than indium and gallium, further one or more kinds selectedfrom tin or germanium are contained, and the content of gallium is from2 to 30% by atom as atom number ratio of Ga/(In+Ga+Sn+Ge), and one ormore kinds selected from tin or germanium is from 1 to 11% by atom asatom number ratio of (Sn+Ge)/(In+Ga+Sn+Ge) (hereafter, this is referredto as a second oxide sintered body).

(I) The First Oxide Sintered Body

The first oxide sintered body of the present invention is characterizedin that, in the oxide sintered body having indium and gallium as anoxide, an In₂O₃ phase with a bixbyite-type structure described in aJCPDS card 06-0416 is a major crystal phase, and a GaInO₃ phase of aβ-Ga₂O₃-type structure described in a JCPDS card 21-0334, or GaInO₃phase and a (Ga, In)₂O₃ phase described in a JCPDS card 14-0564, isfinely dispersed therein as a crystal grain having an average particlediameter of equal to or smaller than 5 μm, and a content of gallium isequal to or higher than 10% by atom and below 35% by atom as atom numberratio of Ga/(In+Ga).

(a) Composition and Oxide Sintered Body Constitution

In the present invention, composition of the first oxide sintered bodyis required that the content of gallium is equal to or higher than 10%by atom and below 35% by atom as atom number ratio of Ga/(In+Ga), forthe transparent conductive film to be obtained by a sputtering method oran ion plating method by using said oxide sintered body, to exhibit lowabsorption of blue light and low resistance.

It is required not only that the oxide sintered body is within the abovecomposition range but also the sintered body constitution has an In₂O₃phase with a bixbyite-type structure as a major crystal phase, and aGaInO₃ phase of a β-Ga₂O₃-type structure, or GaInO₃ phase and a (Ga,In)₂O₃ phase is finely dispersed therein, as a crystal grain having anaverage particle diameter of equal to or smaller than 5 μm.

In the above In₂O₃ phase with a bixbyite-type structure having a solidsolution of gallium, and the GaInO₃ phase of a β-Ga₂O₃-type structureconstituted by indium and gallium, and the (Ga, In)₂O₃ phase, a part ofindium may be substituted with gallium, or a part of gallium may besubstituted with indium, or a certain degree of gap from stoichiometriccomposition or deficit of a metal element or oxygen deficit may beincluded. It should be noted that the (Ga, In)₂O₃ phase is a phaseformed at a high sintering temperature of equal to or higher than 1500°C. in normal pressure sintering. (Ga, In)₂O₃ phase raises no problem, aslong as it is in small quantity, although it provides a little higherelectric resistance and a little lower film-formation rate as comparedwith the GaInO₃ phase.

However, presence of too high quantity raises a problem of decrease infilm-formation rate or decrease in productivity or the like. In order todecrease absorption of blue light of a transparent conductive film, asdescribed also in the above Patent Document 1, inclusion of the GaInO₃phase of a β-Ga₂O₃-type structure constituted by indium and gallium, inthe oxide sintered body to be used as a target for obtaining thetransparent conductive film is required, and still more the (Ga, In)₂O₃phase may be contained.

In addition, as described above, because the first oxide sintered bodyof the present invention has the In₂O₃ phase with a bixbyite-typestructure having a solid solution of gallium as a major phase, and theGaInO₃ phase of a β-Ga₂O₃-type structure constituted by indium andgallium is less, it is characterized in that intensity ratio of X-raydiffraction peaks defined by the following expression (1), is from 8% to58%. The intensity ratio of X-ray diffraction peaks of below 8%decreases excessively the GaInO₃ phase in the oxide sintered body,resulting in too high absorption of blue light by the transparentconductive film, on the other hand, the intensity ratio of X-raydiffraction peaks of over 58% raises a problem of excessive increase inspecific resistance of the transparent conductive film formed, orfrequent generation of arcing in sputtering, and thus not preferable.I[GaInO₃ phase(111)]/{I[In₂O₃ phase(400)]+I[GaInO₃ phase(111)]}×100[%](wherein I[In₂O₃ phase (400)] represents (400) peak intensity of theIn₂O₃ phase with a bixbyite-type structure, and I[GaInO₃ phase (111)]represents (111) peak intensity of a composite oxide of β-GaInO₃ phasewith a β-Ga₂O₃-type structure).(b) Content of Gallium

In the first oxide sintered body, the content of gallium is equal to orhigher than 10% by atom and below 35% by atom as atom number ratio ofGa/(In+Ga).

In the case where the gallium content is below 10% by atom as atomnumber ratio of Ga/(In+Ga), most of the oxide sintered body isconstituted by only the InO₃ phase with a bixbyite-type structure, wheregallium is present as a solid solution. Therefore, that case does notcontain the above composite oxide phase, and thus can not form thetransparent conductive film having the above optical characteristics.

On the other hand, in the case where the gallium content is over 35% byatom as atom number ratio of Ga/(In+Ga), ratio of the GaInO₃ phase of aβ-Ga₂O₃-type structure constituted by indium and gallium and the (Ga,In)₂O₃ phase in the oxide sintered body are included, however, thisratio increases inevitably, and mainly the above two phases are present,where the In₂O₃ phase with a bixbyite-type structure having gallium as asolid solution becomes to be present inevitably. Such an oxide sinteredbody is equivalent to a conventional one of the Patent Document 4, whichincreases the GaInO₃ phase with a β-Ga₂O₃-type structure or the (Ga,In)₂O₃ phase having low film-formation rate in a sputtering method orthe like, therefore decreases inevitably film-formation rate anddecreases industrial production efficiency. In addition, it is difficultthat specific resistance of the transparent conductive film to be formedexhibits equal to or lower than 2×10⁻³ Ω·cm, and still more it is farmore difficult to attain the level of 10⁻⁴ Ω·cm, which is a practicaltarget of the present invention.

(c) A Sintered Body Constitution and a Nodule

In the case where the oxide sintered body of the present invention isprocessed, for example, as a target for direct-current sputtering,crystal grains of the In₂O₃ phase and the GaInO₃ phase, and/or the (Ga,In)₂O₃ phase are present at the target surface, however, in comparisonbased on volume ratio, when content of gallium in the oxide sinteredbody is equal to or higher than 10% by atom and below 35% by atom asatom number ratio of Ga/(In+Ga), volume ratio of the crystal grains ofthe In₂O₃ phase increase, as described above. Such a target usuallynever generates a nodule at the target surface. However, even when anoxide sintered body has indium and gallium within the above composition,a problem of nodule generation at the target surface may happen in somecases.

It is the case where the GaInO₃ phase along with the (Ga, In)₂O₃ phaseare present in a large quantity. The GaInO₃ phase along with the (Ga,In)₂O₃ phase provide higher electric resistance as compared with theIn₂O₃ phase, and are difficult to be sputtered, due to having a strongchemical bond, which is specific to a composite oxide. An oxide sinteredbody of general ITO is constituted by coarse crystal grains of the In₂O₃phase, with an average particle diameter of about 10 μm, however, in thecase where the oxide sintered body containing indium and gallium in theabove composition range is constituted by the coarse crystal grainssimilarly as in ITO, the grains of the In₂O₃ phase are sputteredpreferentially, on the other hand, sputtering of the crystal grains ofthe GaInO₃ phase, or the GaInO₃ phase and the (Ga, In)₂O₃ phase does notprogress, and thus the coarse crystal grains of the GaInO₃ phase, or theGaInO₃ phase and the (Ga, In)₂O₃ phase remain inevitably at the targetsurface without being dug out. Starting from these digging-residuepoints, a nodule tends to grow gradually, by which abnormal dischargesuch as arcing is inevitably generated frequently.

In order to suppress the above digging-residue, that is a nodule, it isrequired to attain a structural refinement of the oxide sintered bodycontaining indium and gallium within the above composition range. Thatis, it is effective that the crystal grain of GaInO₃ phase, or theGaInO₃ phase and the (Ga, In)₂O₃ phase in said oxide sintered body isfinely dispersed. To begin with, because the GaInO₃ phase along with the(Ga, In)₂O₃ phase are conductive bodies, they themselves do not causeabnormal discharge themselves, and finer dispersion thereof makesdifficult for them to become starting points of nodule growth.

FIG. 1 shows a SEM image of the oxide sintered body of the presentinvention, observed with a scanning electron microscope (SEM) of theoxide sintered body containing of gallium in 20% by atom as atom numberratio of Ga/(In+Ga), as an example of finely dispersed crystal grains ofthe GaInO₃ phase, or the GaInO₃ phase and the (Ga, In)₂O₃ phase.Irregular-shaped black particles are dotted with in a white matrix. As aresult of EDS (Energy Dispersive Spectroscopy) analysis, it have beenfound that the black crystal grains are the GaInO₃ phase, or the GaInO₃phase and the (Ga, In)₂O₃ phase, and surrounding white crystal grainsare crystal grains of the In₂O₃ phase. The crystal grains of the GaInO₃phase, or the GaInO₃ phase and the (Ga, In)₂O₃ phase have an averageparticle diameter of equal to or smaller than 5 μm, and in addition, useof a target obtained by processing this oxide sintered body seldomgenerated a nodule starting from the digging-residue. From this fact, itis clear that, a constitution of the In₂O₃ phase finely dispersed withthe GaInO₃ phase, as shown in FIG. 1, is effective in suppression of anodule in sputtering.

Therefore, in order to suppress a nodule, it is required that averageparticle diameter of the crystal grains composed of the GaInO₃ phase, orthe GaInO₃ phase and the (Ga, In)₂O₃ phase is equal to or smaller than 5μm. Still more it is preferable to be controlled at equal to or smallerthan 3 μm. It should be noted that the gallium content in the oxidesintered body of below 10% by atom provides, as described above, asingle In₂O₃ phase structure, therefore a nodule suppression method byfine dispersion of the a crystal grains of the GaInO₃ phase, or theGaInO₃ phase and the (Ga, In)₂O₃ phase of the present invention is noteffective.

In this way, a dispersion state of the GaInO₃ phase, or the GaInO₃ phaseand the (Ga, In)₂O₃ phase in the oxide sintered body is specified, aswell as constitution ratio to the In₂O₃ phase is also specified.Constitution ratio of the In₂O₃ phase of main phase and the GaInO₃ phaseof dispersed phase in the oxide sintered body of the present inventionis from 8% to 58% as intensity ratio of X-ray diffraction peaks definedby the above expression (1). On the contrary, in Patent Document 4 bythe present applicant, gallium content of a sintered body target forproduction of the transparent conductive film is from 35% by atom to 45%by atom as atom number ratio of Ga/(In+Ga)), and the composition rangeis different from that of the present invention, however, it has beendescribed that intensity ratio of X-ray diffraction peaks defined by thefollowing expression (2) is from 50% to 110%, that is, from 48% to 67%when converted to intensity ratio of X-ray diffraction peaks defined bythe above expression (1), and thus the range of the intensity ratio ofX-ray diffraction peaks is partially overlapped with the presentinvention. This is estimated to be influenced mainly by difference ofparticle diameter or dispersing property of the GaInO₃ phase generatedby difference of average particle diameter of raw material powders, anddifference of diffusion behavior in a sintering reaction.I[In₂O₃ phase(400)]/I[GaInO₃ phase(111)]×100[%]  (2)(wherein I[In₂O₃ phase (400)] represents (400) peak intensity of theIn₂O₃ phase with a bixbyite-type structure, and I[GaInO₃ phase (111)]represents (111) peak intensity of a composite oxide of β-GaInO₃ phasewith a β-Ga₂O₃-type structure).

In general, by subjecting the crystal grains constituting an oxidesintered body to refinement, strength enhancement is attained. In thepresent invention as well, because of having the above sintered bodyconstitution, the oxide sintered body becomes difficult to be fractured,even in receiving of impact by heat or the like, caused by increaseddirect-current power charge.

(II) A Second Oxide Sintered Body

In addition, the second oxide sintered body of the present invention isan oxide sintered body containing indium and gallium as an oxide,characterized in that an In₂O₃ phase with a bixbyite-type structure is amajor crystal phase, and a GaInO₃ phase of a β-Ga₂O₃-type structure, ora GaInO₃ phase and a (Ga, In)₂O₃ phase is finely dispersed therein, as acrystal grain having an average particle diameter of equal to or smallerthan 5 μm, and other than indium and gallium, further one or more kindsof additive components selected from tin or germanium are contained, andthe content of gallium is from 2 to 30% by atom as atom number ratio ofGa/(In+Ga+Sn+Ge), and the content of the additive components is from 1to 11% by atom as atom number ratio of (Sn+Ge)/(In+Ga+Sn+Ge).

That is, in the present invention, in the oxide sintered body containingindium and gallium, further one or more kinds of additive components maybe included, which are selected from tin, germanium, silicon, niobium,titanium, zirconium, hafnium, cerium, molybdenum or tungsten. The mosteffective ones as the additive components are tin and germanium. Contentof the additive components is not especially limited, however, it ispreferably from 1 to 11% by atom as atom number ratio of(Sn+Ge)/(In+Ga+Sn+Ge). More preferable content of the additivecomponents is 2 to 10% by atom.

In the case when the oxide sintered body contains one or more kinds ofadditive components selected from tin or germanium, not only specificresistance of the oxide sintered body decreases and film-formation rateenhances but also specific resistance of the transparent conductive filmformed decreases more. In this case, the content of one or more kindsselected from tin or germanium is below 1% by atom as atom number ratioof (Sn+Ge)/(In+Ga+Sn+Ge) does not provide such effect, while the contentover 11% by atom may impair the object of the present invention instead.It should be noted that, in consideration of making specific resistanceof the transparent conductive film formed lower, it is preferable thatthe content of one or more kinds selected from tin or germanium is from2 to 10% by atom as atom number ratio of (Sn+Ge)/(In+Ga+Sn+Ge). Inaddition, in the case where decrease in absorption at a short wavelengthside of a visible region, that is, blue light, under industrially usefulcondition of film-formation at low temperature, is required, theaddition of one or more kinds selected from tin and germanium may impairthe above characteristic in some cases. The reason is considered becausea part of the one or more kinds selected from tin and germanium of anamorphous film formed, may be converted in some cases to SnO and GeOhaving high light absorption, in the case of film-formation at lowtemperature. In the case where one or more kinds selected from tin andgermanium are contained in a range of the above atom ratio, it ispreferable that the content of gallium is from 2 to 30% by atom as atomnumber ratio of Ga/(In+Ga+Sn+Ge). More preferable content of gallium isfrom 2 to 20% by atom. Reason for including lower Ga atom ratio in thecomposition range of the present invention, as compared with the case ofnot containing tin and germanium, is because the above GaInO₃ phase and(Ga, In)₂O₃ phase are formed in a larger quantity, even under the sameGa atom ratio, in the case where tin and germanium are contained. Thecase of lower Ga atom ratio than this range is not preferable, becausethe oxide sintered body is constituted by only the In₂O₃ phase with abixbyite-type structure, where gallium is present as a solid solution,similarly as in the above case of no inclusion of tin and germanium. Onthe other hand, in the case where the ratio is over this range, theGaInO₃ phase, or the GaInO₃ phase and a (Ga, In)₂O₃ phase becomes amajor phase, and the In₂O₃ phase becomes a dispersed phase. When it isused as, for example, a sputtering target in film-formation, it neverraises an outstanding nodule problem originally. In addition, not onlyfilm-formation rate decreases but also showing of decreased specificresistance of the transparent conductive film formed becomes difficult.

In addition, in the case where the one or more kinds selected from tinor germanium are contained within the above atom ratio range, that is,also in the second oxide sintered body similarly as in the first oxidesintered body, the In₂O₃ phase with a bixbyite-type structure, wheregallium is present as a solid solution, is set to be a major phase, andthe GaInO₃ phase of a β-Ga₂O₃-type structure, constituted by indium andgallium, is set to be a dispersed phase. However, a different point fromthe first oxide sintered body is that, by the addition of one or morekinds selected from tin and germanium, orientation tendency generates inthe GaInO₃ phase. Therefore, it is preferable that intensity ratio ofX-ray diffraction peaks is defined by the following expression (3), notby the above expression (1). In this case, intensity ratio of X-raydiffraction peaks defined by the following expression (3), is preferablyfrom 4% to 84%:I[GaInO₃ phase(−111)]/{I[In₂O₃ phase(400)]+I[GaInO₃phase(−111)]}×100[%]  (3)(wherein I[In₂O₃ phase (400)] represents (400) peak intensity of theIn₂O₃ phase with a bixbyite-type structure, and I[GaInO₃ phase (−111)]represents (−111) peak intensity of a composite oxide of β-GaInO₃ phasewith a β-Ga₂O₃-type structure).

In the second oxide sintered body, it is estimated that orientationtendency generates such that the (−111) plane grows preferentially,because of presence of a solid solution of one or more kinds selectedfrom tin and germanium in the GaInO₃ phase. Because of orientationtendency, range of value taken by the intensity ratio of X-raydiffraction peaks defined by the expression (3), becomes apparentlywider than that of the above expression (1). It should be noted that theintensity ratio of X-ray diffraction peaks of below 4% provides too lowGaInO₃ phase in the oxide sintered body, and too high absorption of bluelight by the transparent conductive film, while the ratio of over 84%raises a problem of too high increase in specific resistance of thetransparent conductive film formed, or frequent occurrence of arcing insputtering, and thus not preferable. In addition, in order to suppress anodule, also as for the second oxide sintered body, it is required thataverage particle diameter of the crystal grain composed of the GaInO₃phase, or the GaInO₃ phase and the (Ga, In)₂O₃ phase is equal to orsmaller than 5 μm, and more preferably it is controlled at equal to orsmaller than 3 μm, in the same way as in the first oxide sintered body.

It should be noted that, by the addition of one or more kinds selectedfrom tin and germanium, a different composite oxide phase may generateto some extent in some cases. For example, there is included a compositeoxide phase of a tetragonal crystal system, represented by the generalformula of Ga_(3−x)In_(5+x)Sn₂O₁₆ (0.3<x<1.5), such as aGa_(2.4)In_(5.6)Sn₂O₁₆ phase described in a JCPDS card 51-0204, aGa₂In₆Sn₂O₁₆ phase described in a JCPDS card 51-0205, or aGa_(1.6)In_(6.4)Sn₂O₁₆ phase described in a JCPDS card 51-0206. Thesecomposite oxide phases have equivalent characteristics to the GaInO₃phase, although various characteristics such as conductivity areinferior to the In₂O₃ phase, therefore, dispersion of these phases incertain quantity in the oxide sintered body raises no problem infilm-formation such as sputtering. In addition, there is no problemraised, because equivalent various characteristics are shown by thetransparent conductive film formed. Naturally, it is required foraverage particle diameter of crystal grains of these composite oxidephases in the oxide sintered body to be equal to or smaller than 5 μm,in the same way as in the GaInO₃ phase, and more preferably it iscontrolled at smaller than 3 μm, for suppression of a nodule.

In addition, it is desirable that the oxide sintered body of the presentinvention does not contain Zn substantially. It is because inclusion ofzinc inevitably increases absorption of visible light of the transparentconductive film to be formed by using this as a raw material. The reasonis considered to be derived from the presence of zinc in a metal-likestate in the transparent conductive film, in film-formation at lowtemperature.

It should be noted that, although description was made on tin, germaniumand zinc, in addition to these, for example, silicon, niobium, titanium,zirconium, hafnium, cerium, molybdenum, tungsten, still more iridium,ruthenium, rhenium and the like may be contained as impurity elements.

2. A Production Method for the Oxide Sintered Body

The production method for the oxide sintered body of the presentinvention is a method by mixing the raw material powders containingindium oxide powders and gallium oxide powders, or by adding the tinoxide powders and/or germanium oxide powders into this raw materialpowders, and mixing, and then by compacting the mixed powders andsintering the compact by a normal pressure firing method, or bycompacting and sintering the mixed powders by a hot press method,characterized by obtaining of the oxide sintered body, where the In₂O₃phase with a bixbyite-type structure becomes a major crystal phase, andthe crystal grain composed of the GaInO₃ phase, or the GaInO₃ phase andthe (Ga, In)₂O₃ phase is finely dispersed therein, having an averageparticle diameter of equal to or smaller than 5 μm, by adjusting theaverage particle diameter of the raw material powders to equal to orsmaller than 1 μm.

That is, performance of the oxide sintered body having the above phaseconstitution and a composition of each phase largely depends onproduction condition of the oxide sintered body, for example, particlediameter of raw material powders, mixing condition and firing condition.

It is required that the oxide sintered body of the present inventionuses indium oxide powders and gallium oxide powders which are adjustedto have an average particle diameter of equal to or smaller than 1 μm,as raw material powders. As the constitutions of oxide sintered body ofthe present invention, it is preferable that the In₂O₃ phase is the mainphase, and the constitution where average particle diameter of thecrystal grains composed of the GaInO₃ phase, or the GaInO₃ phase and the(Ga, In)₂O₃ phase is equal to or smaller than 5 μm is present together.The constitution is more preferable that the crystal grains composed ofthe GaInO₃ phase, or the GaInO₃ phase and the (Ga, In)₂O₃ phase isfinely dispersed in the main phase, and an average particle diameter isequal to or smaller than 3 μm. It should be noted that certain separatecomposite oxides, which may generate in the second oxide sintered body,for example, a Ga_(2.4)In_(5.6)Sn₂O₁₆ phase, a Ga₂In₆Sn₂O₁₆ phase and aGa_(1.6)In_(6.4)Sn₂O₁₆ phase or the like are preferably the same fineconstitutions.

In order to form such fine constitutions, it is required for averageparticle diameter of raw material powders to be adjusted to equal to orsmaller than 1 μm. Use of indium oxide powders and gallium oxide powdershaving the average particle diameter of over 1 μm as raw materialpowders, inevitably increases average particle diameter of crystalgrains composed of the GaInO₃ phase, or the GaInO₃ phase and the (Ga,In)₂O₃ phase, which are present with the In₂O₃ phase as a main phase inthe obtained oxide sintered body, to over 5 μm. As described above,large crystal grains of the GaInO₃ phase, or the GaInO₃ phase and the(Ga, In)₂O₃ phase, with the average particle diameter of over 5 μm, aredifficult to be sputtered, and by continuing the sputtering, becomerelatively large residue at the target surface, which becomes a startingpoint of a nodule, causing abnormal discharge such as arcing. In theabove Patent Document 4, although presence of the crystal grainscomposed of the GaInO₃ phase, or the GaInO₃ phase and the (Ga, In)₂O₃phase has been shown, however, relationship between the crystal grainconstitutions and nodule suppression has not been noticed.

Indium oxide powders are raw materials of ITO (indium-tin oxide), anddevelopment of fine indium oxide powders having excellent sinteringproperty, has been progressed with improvement of ITO. And, the rawmaterial powders with an average particle diameter of equal to orsmaller than 1 μm, are easily available, due to use in a large quantityat present, as raw materials of ITO. However, in the case of galliumoxide powders, raw material powders with an average particle diameter ofequal to or smaller than 1 μm are not easily available, due to smalleruse quantity as compared with indium oxide powders. Therefore the coarsegallium oxide powders are required to be crushed to an average particlediameter of equal to or smaller than 1 μm. In addition, tin oxidepowders and germanium oxide powders to be added for obtaining of thesecond oxide sintered body, are in a similar situation as each of thecases of the indium oxide powders and the gallium oxide powders, and thegermanium oxide powders are required to be crushed from coarse powdersto an average particle diameter of equal to or smaller than 1 μm.

In order to obtain the oxide sintered body of the present invention,after mixing the raw material powders containing indium oxide powdersand gallium oxide powders, the mixed powder are compacted and thecompact is sintered by a normal pressure firing method, or the mixedpowders are compacted and sintered by a hot press method. The normalpressure firing method is a simple and convenient, and industriallyadvantageous method, and thus a preferable method, however, a hot pressmethod may be used as well, if necessary.

In the case where the normal pressure firing method is used, a compactis prepared first. Raw material powders are charged into a resin pot formixing along with a binder (for example, PVA) or the like, by using awet-type ball mill or the like. In order to obtain the oxide sinteredbody of the present invention, where average particle diameter ofcrystal grains composed of the GaInO₃ phase, or the GaInO₃ phase and the(Ga, In)₂O₃ phase, which are present with the In₂O₃ phase as a mainphase, is equal to or smaller than 5 μm, and the crystal grains arefinely dispersed, it is preferable that the above ball mill mixing isperformed for equal to or longer than 18 hours. In this case, as a ballfor mixing, a hard-type ZrO₂ ball may be used. After the mixing, slurryis taken out for performing of filtration, drying and granulation. Afterthat, the obtained granulated substances are compacted, under a pressureof from about 9.8 MPa (0.1 ton/cm²) to 294 MPa (3 ton/cm²), by using acold isostatic press to obtain a compact.

In a sintering step of the normal pressure firing method, heating isperformed at a predetermined temperature range under atmosphere ofoxygen presence. The temperature range is determined whether thesintered body is used for sputtering or for ion plating. In the case ofuse for sputtering, sintering is performed at 1250 to 1450° C., morepreferably at 1300 to 1400° C., under atmosphere where oxygen gas isintroduced into air inside a sintering furnace. Sintering time ispreferably from 10 to 30 hours, and more preferably from 15 to 25 hours.

On the other hand, in the case of use for ion plating, a compact issintered at 1000 to 1200° C., for 10 to 30 hours under atmosphere ofoxygen presence, preferably at 1000 to 1100° C., under atmosphere whereoxygen gas is introduced into air inside a sintering furnace. Sinteringtime is preferably from 15 to 25 hours.

By using the indium oxide powders and gallium oxide powders, which areadjusted to have the above average particle diameter of equal to orsmaller than 1 μm, and at the sintering temperature of the above range,as raw material powders, it is possible to obtain a dense oxide sinteredbody, where the crystal grains composed of the GaInO₃ phase, or theGaInO₃ phase and the (Ga, In)₂O₃ phase having an average particlediameter of equal to or smaller than 5 μm, more preferably equal to orsmaller than 3 μm, are finely dispersed in the In₂O₃ phase matrix.

The too low sintering temperature does not progress a sintering reactionsufficiently. In particular, in order to obtain the oxide sintered bodywith a density of equal to or higher than 6.0 g/cm³, the temperature ispreferably equal to or higher than 1250° C. On the other hand, thesintering temperature over 1450° C. extremely increases formation of the(Ga, In)₂O₃ phase, decreases volume ratio of the In₂O₃ phase and theGaInO₃ phase, which makes difficult control of the oxide sintered bodyto the above finely dispersed constitution.

Sintering atmosphere is preferably atmosphere in the presence of oxygen,and still more preferably atmosphere where oxygen gas is introduced intoair inside the sintering furnace. Presence of oxygen in sinteringenables to make higher density of the oxide sintered body. In raising atemperature to sintering temperature, in order to prevent cracking of asintered body and progress de-binder, it is preferable to settemperature increasing rate in a range of from 0.2 to 5° C./min. Inaddition, if necessary, different temperature increasing rates may becombined to raise temperature up to sintering temperature. In the stepfor increasing temperature, specific temperature may be held for acertain period aiming at progressing of de-binder or sintering. Incooling after sintering, it is preferable to stop introduction ofoxygen, and lower temperature down to 1000° C. at temperature decreasingrate in a range of from 0.2 to 5° C./min, in particular, equal to orhigher than 0.2° C./min and lower than 1° C./min.

In the present invention, in the case where a hot press method isadopted, the mixed powders are compacted and sintered at 700 to 950° C.for 1 to 10 hours under a pressure of 2.45 to 29.40 MPa in inert gasatmosphere or in vacuum. The hot press method can decrease the oxygencontent in the sintered body, due to subjecting raw material powders ofthe oxide sintered body to compacting and sintering under reducingatmosphere, as compared with the above normal pressure firing method.However, caution is required at a high temperature of over 950° C.,because of reduction of indium oxide and melting as metal indium.

One Example of production condition of the oxide sintered body by thehot press method of the present invention is shown. That is, indiumoxide powders with an average particle diameter of equal to or smallerthan 1 μm, along with gallium oxide powders with an average particlediameter of equal to or smaller than 1 μm, or still more tin oxidepowders with an average particle diameter of equal to or smaller than 1μm, or germanium oxide powders with an average particle diameter ofequal to or smaller than 1 μm are prepared, as raw material powders, soas to be predetermined ratio.

The prepared raw materials are sufficiently mixed similarly as in ballmill mixing of a normal pressure firing method, preferably for a mixingtime of equal to or longer than 10 hours, to obtain granulatedsubstance. Then the granulated mixed powders are supplied into a carboncontainer to be subjected to sintering by the hot press method.Sintering temperature may be set at from 700 to 950° C., pressure may beset at from 2.45 MPa to 29.40 MPa (25 to 300 kgf/cm²), and sinteringtime may be set from about 1 to 10 hours. Atmosphere during hot press ispreferably in inert gas such as Ar, or in vacuum.

In the case of obtaining a target for sputtering, more preferably,sintering temperature may be set at from 800 to 900° C., pressure may beat from 9.80 MPa to 29.40 MPa (100 to 300 kgf/cm²), and sintering timemay be from 1 to 3 hours. In addition, in the case of obtaining a targetfor ion plating, more preferably, sintering temperature may be set atfrom 700 to 800° C., pressure may be at from 2.45 MPa to 9.80 MPa (25 to100 kgf/cm²), and sintering time may be from 1 to 3 hours.

It should be noted that, in Patent Document 2, there has been described,on preparation condition of the oxide sintered body, that each powdersof Ga₂O₃ and In₂O₃ were mixed uniformly in a molar fraction of 33.0 and67% by mol, respectively, and then fired at 1000° C. for 5 hours inargon (Example 1). However, there has been no description on averageparticle diameter of powders of Ga₂O₃ and In₂O₃, and firing wasperformed at a relatively low temperature of 1000° C. Because a targetproduced in this way has low density due to no progress of sintering,arcing generates frequently in charging of high direct-current power insputtering. In addition, because of no description, in particular, onadjustment of Ga₂O₃ powders to fine powders or the like, it is estimatedthat coarse powders with an average particle diameter of over 1 μm areused, and in this case, a constitution of the oxide sintered body as araw material has crystal grains composed of the GaInO₃ phase, or theGaInO₃ phase and the (Ga, In)₂O₃ phase, having an average particlediameter of far over 5 μm, and a nodule generates by sputtering underenhanced film-formation rate.

3. A Target

The target of the present invention may be obtained by cutting the aboveoxide sintered body to predetermined dimension and by processing bysurface grinding and then by adhering to a backing plate. The target inthe present invention includes a target for sputtering and a target forion plating.

In the case of the target for sputtering, density thereof is preferablyequal to or higher than 6.3 g/cm³. The density of below 6.3 g/cm³generates cracks or fractures, causing generation of nodules. Inaddition, in the case of use for a target for ion plating, it ispreferable that density is controlled at 3.4 to 5.5 g/cm³. The densitybelow 3.4 g/cm³ provides inferior strength of a sintered body itself,and thus cracks or fractures easily generate even for small and localthermal expansion. The density of over 5.5 g/cm³ makes impossible toabsorb stress or strain generated locally in charging of electron beams,and cracks generate easily.

It is due to this reason for difference of firing condition for betweena target for sputtering and a target for ion plating, in a productionmethod for the above oxide sintered body. For sputtering, it ispreferable that by adoption of a normal pressure firing method, acompact is sintered at 1250 to 1450° C. for 10 to 30 hours, inatmosphere in the presence of oxygen; or by adoption of a hot pressmethod, mixed powders are sintered at 700 to 950° C. for 1 to 10 hoursunder a pressure of 2.45 to 29.40 MPa, in inert gas atmosphere or invacuum. In addition, for ion plating, it is preferable that by adoptionof a normal pressure firing method, a compact is sintered at 1000 to1200° C. for 10 to 30 hours, in atmosphere in the presence of oxygen, sothat density range becomes lower than target for sputtering, asdescribed above.

4. A Transparent Conductive Film Containing Indium and Gallium, and aFilm-Formation Method Therefor

The transparent conductive film of the present invention is an amorphoustransparent conductive film obtained by forming on a substrate, by asputtering method or an ion plating method, by using the above target.

In the transparent conductive film of the present invention, there aretwo kinds: one having a content of gallium is equal to or higher than10% by atom and below 35% by atom as atom number ratio of Ga/(In+Ga)(hereafter, this is referred to as a first oxide sintered body); and onewhere, other than indium and gallium, further one or more kinds selectedfrom tin or germanium are contained, and the content of gallium is from2 to 30% by atom as atom number ratio of Ga/(In+Ga+Sn+Ge), and thecontent of one or more kinds selected from tin or germanium is from 1 to11% by atom as atom number ratio of (Sn+Ge)/(In+Ga+Sn+Ge) (hereafter,this is referred to as a second oxide sintered body).

In a sputtering method or the like for film-formation of a transparentconductive film, increase in direct-current power is performed generallyto enhance film-formation rate. In the present invention, the firstoxide sintered body containing indium and gallium has, as describedabove, crystal grains of the In₂O₃ phase and the GaInO₃ phase, or theIn₂O₃ phase and the GaInO₃ phase and the (Ga, In)₂O₃ phase in said oxidesintered body, are refined and content of gallium in the oxide sinteredbody is 10% by atom to 30% by atom as atom number ratio of Ga/(In+Ga);and in addition, the second oxide sintered body has content of galliumof from 2 to 30% by atom as atom number ratio of Ga/(In+Ga+Sn+Ge), andthe content of one or more kinds selected from tin and germanium of from1 to 11% by atom as atom number ratio of (Sn+Ge)/(In+Ga+Sn+Ge).

Because the GaInO₃ phase and the (Ga, In)₂O₃ phase are finely dispersedin the In₂O₃ phase, it makes difficult for them to become startingpoints of nodule growth, and thus nodule generation is suppressed evenwhen direct-current power to be charged is increased, which, as aresult, enables to suppress abnormal discharge such as arcing.

In the case where the transparent conductive film of the presentinvention is formed on a substrate by a sputtering method, inparticular, in the case of a direct-current (DC) sputtering method,there is no thermal influence in film-formation, and high ratefilm-formation is possible, and thus it is industrially advantageous. Inorder to form the oxide sintered body of the present invention by adirect-current sputtering method, it is preferable to use mixed gascomposed of inert gas and oxygen, in particular, argon and oxygen, assputtering gas. In addition, it is preferable that sputtering isperformed by setting of pressure inside a chamber of a sputteringapparatus at from 0.1 to 1 Pa, in particular, from 0.2 to 0.8 Pa.

In the present invention, for example, pre-sputtering may be performed,after vacuum exhaustion, for example, down to equal to or lower than2×10⁻⁴ Pa, by introduction of mixed gas composed of argon and oxygen toset the gas pressure at from 0.2 to 0.5 Pa, and by application ofdirect-current power so that direct-current power to the target area,that is, direct-current power density, is in a range of from about 1 to3 W/cm², to generate direct-current plasma. After performing of thispre-sputtering for from 5 to 30 minutes, it is preferable to performsputtering by correction of a substrate position, if necessary.

In the present invention, film-formation is possible at room temperaturewithout heating the substrate, however, the substrate may be heated atfrom 50 to 300° C., in particular, from 80 to 200° C. In the case wherethe substrate is one with low melting point, such as a resin plate, aresin film, it is desirable to perform film-formation without heating.Use of a sputtering target prepared from the above oxide sintered bodyof the present invention enables to produce the oxide sintered body withexcellent optical characteristics and conductivity on the substrate, bya direct-current sputtering method, in relatively high film-formationrate.

In addition, also in the case of using a target for ion plating (it maybe called a tablet or a pellet) prepared from the above oxide sinteredbody, a transparent conductive film can be formed similarly. In an ionplating method, as described above, irradiation of electron beams orheat by arc discharge or the like onto a target to become an evaporationsource, raises temperature locally at a part irradiated, by whichparticles are evaporated and deposited onto a substrate. In this case,evaporated particles are ionized by electron beams or arc discharge.There are various methods for ionization, however, a high density plasmaassisted vapor deposition method (HDPE method) using a plasma generationapparatus (a plasma gun) is suitable for forming a transparentconductive film with good quality. In this method, arc discharge byusing the plasma gun is utilized. Arc discharge is maintained between abuilt-in cathode in said plasma gun and an evaporation source crucible(anode). By introducing the electrons emitted from the cathode into thecrucible by magnetic deflection, irradiation is concentrated locallyonto the target incorporated in the crucible. By this electron beams,particles are evaporated from a locally high temperature part, anddeposited onto the substrate. Because evaporated particles thusvaporized or O2 gas introduced as reaction gas is ionized and activatedin this plasma, a transparent conductive film with good quality can beprepared.

The transparent conductive film of the present invention is prepared byusing a target prepared by processing the oxide sintered body of thepresent invention, and by the above sputtering method or ion platingmethod, and is present in an amorphous state irrespective of substratetemperature.

In general, an ITO film becomes a crystalline state when the substratetemperature is increased to about 200° C., although it shows anamorphous state at room temperature. However, the transparent conductivefilm of the present invention keeps an amorphous state, even when thesubstrate temperature is increased to 300° C. As reason for keeping anamorphous state even at high temperature, it is considered that there ispresent, in the oxide sintered body as a raw material of the presentinvention, the finely dispersed GaInO₃ phase, or GaInO₃ phase and (Ga,In)₂O₃ phase, in an average particle diameter of equal to or smallerthan 5 μm, preferably equal to or smaller than 3 μm. It is consideredthat, in the transparent conductive film of the present invention, anamorphous part derived from a composite oxide phase finely dispersedwith these, and an amorphous part derived from the In₂O₃ phase arepresent together. It is estimated that because the former does notcrystallize so easily, even at a high temperature of over 400° C., thelatter, which originally tends to crystallize easily, can notcrystallize.

Because the transparent conductive film of the present invention is anamorphous film, as described above, therefore arithmetic average heightRa, representing surface roughness, is equal to or lower than 1.0 nm,and is very flat. A film having such flat surface is suitable toapplications such as organic EL, which dislikes leakage caused by filmirregularity. In addition, an amorphous transparent conductive film hasadvantage of no generation of a residue in wet-etching. Therefore, it isparticularly advantageous in applications of TFT of a liquid crystaldevice and the like, where thinning of wiring patterning of thetransparent conductive film is progressing.

Thickness of the transparent conductive film of the present invention isnot especially specified, because it differs depending on applications,however, it is from 10 to 500 nm, and preferably from 50 to 300 nm. Thethickness below 10 nm may not ensure sufficient specific resistance,while the thickness over 500 nm results in raising a problem of coloringof the film, and thus not preferable.

In addition, average transmittance in a visible region (400 to 800 nm)of the transparent conductive film of the present invention is equal toor higher than 80%, preferably equal to or higher than 85% and stillmore preferably equal to or higher than 90%. The average transmittanceof below 80% makes applications to an organic EL element and the likedifficult.

The transparent conductive film of the present invention has low lightabsorption, in particular, at a short wavelength side of a visibleregion, and high transmittance. Usually, an ITO film formed at roomtemperature has high light absorption at a short wavelength side of awavelength of around 400 nm, and extinction coefficient at a wavelengthof 400 nm is over 0.04. On the contrary, the transparent conductive filmof the present invention shows extinction coefficient at a wavelength of400 nm of equal to or smaller than 0.04, and it becomes equal to orlower than 0.03, in the case where content of gallium is equal to orhigher than 20% by atom and below 35% by atom as atom number ratio ofGa/(In+Ga), in the first transparent conductive film. Therefore, it issuitable as a transparent electrode of a blue LED, which emits light ofa wavelength of about 400 nm.

In general, in order to use a transparent conductive film in wideapplication fields, it is preferable that specific resistance is equalto or lower than 2×10⁻³ Ω·cm. In the applications of the above liquidcrystal device or blue LED or the like, specific resistance is requiredto be below 1×10⁻³ Ω·cm. Specific resistance of the transparentconductive film obtained by using the oxide sintered body containingindium and gallium of the present invention, decreases by increase inthe In component. Because the transparent conductive film of the presentinvention shows a specific resistance of equal to or lower than 2×10⁻³Ω·cm, applications to various devices are possible. Further, in thefirst transparent conductive film having composition range where contentof gallium is 10 to 25% by atom as atom number ratio of Ga/(In+Ga),specific resistance exhibits below 1×10⁻³ Ω·cm, in addition, in thesecond transparent conductive film, in the case where the content ofgallium is from 2 to 20% by atom as atom number ratio ofGa/(In+Ga+Sn+Ge), and the content of the additive components is from 2to 10% by atom as atom number ratio of (Sn+Ge)/(In+Ga+Sn+Ge), specificresistance exhibits similarly below 1×10⁻³ Ω·cm, and also superiority ofoptical characteristics at the above short wavelength side of a visibleregion is maintained, which therefore provides usefulness inapplications, in particular, for a blue LED and the like.

5. A Transparent Conductive Substrate

In the transparent conductive substrate of the present invention, theabove transparent conductive film is formed on one surface or bothsurfaces of the transparent substrate. The transparent substrate isusually selected from a glass plate, a quartz plate, a resin plate or aresin film.

This transparent conductive substrate is one to have the abovetransparent conductive film function as an anode and/or a cathode of adisplay panel such as LCD, PDP or an EL element. Because the substratealso functions as a light transmittable supporting body, it is requiredto have a certain strength and transparency.

As a material constituting the resin plate or the resin film, there maybe included polyethyleneterephtharate (PET), polyethersulfone (PES),polyarylate (PAR), polycarbonate (PC) or the like, and it may be theresin plate or the resin film having a structure covered with an acrylicresin on the surface thereof.

Thickness of the substrate is not especially limited, however, it is setto be from 0.5 to 10 mm, preferably from 1 to 5 mm for the glass plateor the quartz plate, and for the resin plate or the resin film, from 0.1to 5 mm, preferably from 1 to 3 mm. Thinner thickness than this rangedecreases strength and makes handling thereof difficult, while thickerthickness than this range not only deteriorates transparency but alsomakes heavy, and thus not preferable.

On the above substrate, there may be formed any of an insulation layer,a semiconductor layer, a gas barrier layer, or a protection layer madeof a single layer or a multi-layer. As the insulation layer, a siliconoxide (Si—O) layer or a silicon oxynitride (Si—O—N) layer or the like isincluded; as the semiconductor layer, a thin film transistor (TFT) orthe like is included, which is mainly formed on a glass substrate; asthe gas barrier layer, there is formed a silicon oxide (Si—O) film,silicon oxynitride (Si—O—N) film, a magnesium aluminate (Al—Mg—O) film,or a tin oxide-type (for Example, Sn—Si—O) film or the like as a steambarrier film, on the resin plate or the resin film. The protection layeris one to protect the substrate surface from scratch or impact, andvarious coatings such as an Si-type, a Ti-type, an acrylic resin-typeare used. It should be noted that a layer formable on the substrate isnot limited thereto, and a thin metal film having conductivity may alsobe applied.

The transparent conductive substrate obtained by the present inventionis extremely useful as constitution parts of various display panels,because a transparent conductive film having excellent characteristicsin view of specific resistance, light transmittance, surface flatness orthe like, is formed thereon. In addition, as surface mounted parts in anelectronic circuit provided with the above transparent conductivesubstrate, laser parts and the like other than an organic EL element areincluded.

EXAMPLES

Explanation will be given below in more detail with reference to Exampleof the present invention, however, the present invention should not belimited to these Example.

<Evaluation of an Oxide Sintered Body>

By using the end material of the oxide sintered body obtained, densityof the sintered body was determined by the Archimedes' method.Subsequently a part of the end material was crushed to performidentification of generated phases by a powder method, with an X-raydiffraction apparatus (manufactured by Philips Co., Ltd.). Then as forthe oxide sintered body containing indium and gallium as oxides,intensity ratio of X-ray diffraction peaks defined by the followingexpression (1) was determined.I[GaInO₃ phase(111)]/{I[In₂O₃ phase(400)]+I[GaInO₃phase(111)]}×100[%]  (1)

It should be noted that, as for the oxide sintered bodies (Examples 8,11 to 15), containing further one or more kinds of additive componentsselected from tin or germanium, other than indium and gallium, intensityratio of X-ray diffraction peaks, defined by the following expression(3) was determined.I[GaInO₃ phase(−111)]/{I[In₂O₃ phase(400)]+I[GaInO₃phase(−111)]}×100[%]  (3)(wherein I[In₂O₃ phase (400)] represents (400) peak intensity of theIn₂O₃ phase with a bixbyite-type structure, and I[GaInO₃ phase (111)] orI[GaInO₃ phase (−111)] represents (111) or (−111) peak intensity of acomposite oxide of β-GaInO₃ phase with a β-Ga₂O₃-type structure,respectively).

By using a part of the powders, composition analysis of the oxidesintered body was performed by an ICP emission spectroscopy. Further,using with SEM (manufactured by Carl Zeiss Japan Co., Ltd.),constitution observation of the oxide sintered body was performed. Fromthe image analysis result of SEM image, average particle diameter of thecrystal grains composed of the GaInO₃ phase was determined.

<Evaluation of Fundamental Characteristics of a Transparent ConductiveFilm>

Composition of the obtained transparent conductive film was studied byan ICP emission spectroscopy. Film thickness of the transparentconductive film was measured with a surface roughness tester(manufactured by Tencor Japan Corp.). Film-formation rate was calculatedfrom film thickness and film-formation time. Specific resistance of thefilm was calculated from a product of surface resistance measured by afour-probe method and film thickness.

Generated phases of the film were identified by X-ray diffractionmeasurement, similarly for the oxide sintered body. In addition,extinction coefficient was measured by using the Spectro Elipsometer(manufactured by J. A. Woolam Co., Ltd.), and in order to evaluateabsorption characteristics of, in particular, blue light, extinctioncoefficient of a wavelength of 400 nm was compared.

Example 1

Zinc oxide powders and gallium oxide powders were adjusted to have anaverage particle diameter of equal to or smaller than 1 μm to prepareraw material powders. These powders were formulated, so that content ofgallium is 10% by atom as atom number ratio represented by Ga/(In+Ga),and charged in a pot made of a resin, together with water to mix in awet-type ball mill. In this case, hard-type ZrO2 balls were used, andmixing time was set to 18 hours. After the mixing, slurry was taken out,filtered, dried and granulated. The granulated substances were convertedto a compact under a pressure of 3 tons/cm², by using a cold isostaticpress.

Then, the compact was sintered as follows. Sintering was performed underatmosphere by introduction of oxygen into a sintering furnace in a rateof 5 L/minute per 0.1 m³ of furnace volume, at a sintering temperatureof 1400° C. for 20 hours. In this case, temperature increasing rate was1° C./minute, and in cooling after sintering, oxygen introduction wasstopped, and temperature was cooled to 1000° C., at a rate of 10°C./minute. The obtained oxide sintered body was processed to a size of152 mm in diameter and 5 mm in thickness, and the sputtering surfacethereof was polished by using a cup grinding stone so that Rz of maximalheight becomes equal to or lower than 3.0 μm. The processed oxidesintered body was subjected to bonding to a backing plate made ofoxygen-free copper using metal indium, to prepare a target forsputtering.

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure constituted by indium and gallium, and the (Ga,In)₂O₃ phase. Intensity ratio of X-ray diffraction peak of the GaInO₃phase (111) represented by the above expression (1) was 8%.

Density of the oxide sintered body was measured and found to be 6.97g/cm³. Subsequently, constitution observation of the oxide sintered bodywas performed with SEM, and found that average particle diameter of theGaInO₃ phase was 2.9 μm.

Next, the above sputtering target was attached to a cathode for anon-magnetic body target of a direct-current magnetron sputteringapparatus (manufactured by ANELVA Corp.) provided with a direct-currentpower source not having arcing suppression function. A non-alkali glasssubstrate (Corning #7059) was used as a substrate, and distance betweenthe target and the substrate was fixed to 60 mm. Mixed gas of argon andoxygen was introduced, so that ratio of oxygen was 1.5%, after vacuumexhausting to below 1×10⁻⁴ Pa, to adjust gas pressure to 0.5 Pa. Itshould be noted that in the above ratio of oxygen of 1.5%, specificresistance exhibited the lowest value.

A direct-current power of 200 W (1.10 W/cm²) was applied to generatedirect-current plasma to perform sputtering. The direct-currentsputtering was performed continuously till attaining of an integratedcharge power value of 12.8 KWh, which is calculated from a product ofdirect-current power charged and sputtering time. Arcing did notgenerate during this period, and discharge was stable. After completionof sputtering, the target surface was observed and found no particularnodule generation. Then by changing the direct-current power to 200,400, 500, 600 W (1.10 to 3.29 W/cm²), sputtering was performed for 10minutes under each power to measure arcing generation times. Under anypower, arcing did not generate and average arcing generation times per 1minute under each direct-current power were zero.

Subsequently, film-formation was performed by direct-current sputtering.After pre-sputtering for 10 minutes, the substrate was allocated justover the sputtering target, that is, at a stationary opposed position,and sputtering was performed at room temperature without heating to forma transparent conductive film with a film thickness of 200 nm. It wasconfirmed that the composition of the obtained transparent conductivefilm was nearly the same as that of the target. By measurement offilm-formation rate, it was confirmed to be 93 nm/minute. Then, bymeasurement of specific resistance of the film, it was confirmed to be4.9×10⁻⁴Ω·cm. Generated phases of the film were identified by X-raydiffraction measurement, and confirmed to be amorphous. In addition,extinction coefficient of a wavelength of 400 nm was measured and foundto be 0.03198. The above evaluation results of a target and evaluationresults of film-formation are shown in Table 1.

Example 2

An oxide sintered body was prepared by a similar method as in Example 1,without changing the condition except that the content of gallium asatom number ratio represented by Ga/(In+Ga) was changed to 20% by atom.

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure constituted by indium and gallium, and the (Ga,In)₂O₃ phase. Then, an X-ray diffraction chart of the oxide sinteredbody is shown in FIG. 2. Intensity ratio of X-ray diffraction peak ofthe GaInO₃ phase (111) represented by the above expression (1) was 30%.Density of the oxide sintered body was measured and found to be 6.84g/cm³. Subsequently, constitution observation of the oxide sintered bodywas performed with SEM, and found that average particle diameter of theGaInO₃ phase was 2.6 μm.

The direct-current sputtering was performed till attaining of anintegrated charge power value of 12.8 KWh, by using this oxide sinteredbody as a sputtering target. Arcing did not generate during this period,and discharge was stable. After completion of sputtering, the targetsurface was observed and found no particular nodule generation. Then bychanging the direct-current power to 200, 400, 500, 600 W (1.10 to 3.29W/cm²), sputtering was performed for 10 minutes under each power tomeasure arcing generation times. FIG. 3 shows arcing generation timesper 1 minute under each direct-current power. Under any power, arcingdid not generate and average arcing generation times per 1 minute undereach direct-current power were zero. Subsequently, film-formation wasperformed by direct-current sputtering. It was confirmed that thecomposition of the obtained transparent conductive film was nearly thesame as that of the target. By measurement of film-formation rate, itwas confirmed to be 86 nm/minute. Then, by measurement of specificresistance of the film, it was confirmed to be 7.8×10⁻⁴ Ω·cm. Generatedphases of the film were identified by X-ray diffraction measurement, andconfirmed to be amorphous. In addition, extinction coefficient of awavelength of 400 nm was measured and found to be 0.02769.

The above evaluation results of a target and evaluation results offilm-formation are shown in Table 1.

Example 3

An oxide sintered body was prepared by a similar method as in Example 1,without changing the condition except that the content of gallium asatom number ratio represented by Ga/(In+Ga) was changed to 25% by atom.

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure constituted by indium and gallium, and the (Ga,In)₂O₃ phase. Intensity ratio of X-ray diffraction peak of the GaInO₃phase (111) represented by the above expression (1) was 39%. Density ofthe oxide sintered body was measured and found to be 6.77 g/cm³.Subsequently, constitution observation of the oxide sintered body wasperformed with SEM, and found that average particle diameter of theGaInO₃ phase was 2.5 μm.

The direct-current sputtering was performed till attaining of anintegrated charge power value of 12.8 KWh, by using this oxide sinteredbody as a sputtering target. Arcing did not generate during this period,and discharge was stable. After completion of sputtering, the targetsurface was observed and found no particular nodule generation. Then bychanging the direct-current power to 200, 400, 500, 600 W (1.10 to 3.29W/cm²), sputtering was performed for 10 minutes under each power tomeasure arcing generation times. Under any power, arcing did notgenerate and average arcing generation times per 1 minute under eachdirect-current power were zero.

Subsequently, film-formation was performed by direct-current sputtering.It was confirmed that the composition of the obtained transparentconductive film was nearly the same as that of the target. Bymeasurement of film-formation rate, it was confirmed to be 86 nm/minute.Then, by measurement of specific resistance of the film, it wasconfirmed to be 8.8×10⁻⁴ Ω·cm. Generated phases of the film wereidentified by X-ray diffraction measurement, and confirmed to beamorphous. In addition, extinction coefficient of a wavelength of 400 nmwas measured and found to be 0.02591.

The above evaluation results of a target and evaluation results offilm-formation are shown in Table 1.

Example 4

An oxide sintered body was prepared by a similar method as in Example 1,without changing the condition except that the content of gallium asatom number ratio represented by Ga/(In+Ga) was changed to 30% by atom.

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure constituted by indium and gallium, and the (Ga,In)₂O₃ phase. Intensity ratio of X-ray diffraction peak of the GaInO₃phase (111) represented by the above expression (1) was 49%. Density ofthe oxide sintered body was measured and found to be 6.70 g/cm³.Subsequently, constitution observation of the oxide sintered body wasperformed with SEM, and found that average particle diameter of theGaInO₃ phase was 2.8 μm.

The direct-current sputtering was performed till attaining of anintegrated charge power value of 12.8 KWh, by using this oxide sinteredbody as a sputtering target. Arcing did not generate during this period,and discharge was stable. After completion of sputtering, the targetsurface was observed and found no particular nodule generation. Then bychange of direct-current power to 200, 400, 500, 600 W (1.10 to 3.29W/cm²), sputtering was performed for 10 minutes under each power tomeasure arcing generation times. Under any power, arcing did notgenerate and average arcing generation times per 1 minute under eachdirect-current power were zero.

Subsequently, film-formation was performed by direct-current sputtering.It was confirmed that the composition of the obtained transparentconductive film was nearly the same as that of the target. Bymeasurement of film-formation rate, it was confirmed to be 84 nm/minute.Then, by measurement of specific resistance of the film, it wasconfirmed to be 1.4×10⁻³ Ω·cm. Generated phases of the film wereidentified by X-ray diffraction measurement, and confirmed to beamorphous. In addition, extinction coefficient of a wavelength of 400 nmwas measured and found to be 0.02361. The above evaluation results of atarget and evaluation results of film-formation are shown in Table 1.

Example 5

An oxide sintered body was prepared by a similar method as in Example 1,without changing the condition except that the content of gallium asatom number ratio represented by Ga/(In+Ga) was changed to 34% by atom.

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure, constituted by indium and gallium, and the (Ga,In)₂O₃ phase. Intensity ratio of X-ray diffraction peak of the GaInO₃phase (111) represented by the above expression (1) was 58%. Density ofthe oxide sintered body was measured and found to be 6.63 g/cm³.Subsequently, constitution observation of the oxide sintered body wasperformed with SEM, and found that average particle diameter of theGaInO₃ phase was 4.1 μm.

The direct-current sputtering was performed till attaining of anintegrated charge power value of 12.8 KWh, by using this oxide sinteredbody as a sputtering target. Arcing did not generate during this period,and discharge was stable. After completion of sputtering, the targetsurface was observed and found no particular nodule generation. Then bychange of direct-current power to 200, 400, 500, 600 W (1.10 to 3.29W/cm²), sputtering was performed for 10 minutes under each power tomeasure arcing generation times. Under any power, arcing did notgenerate and average arcing generation times per 1 minute under eachdirect-current power were zero.

Subsequently, film-formation was performed by direct-current sputtering.It was confirmed that the composition of the obtained transparentconductive film was nearly the same as that of the target. Bymeasurement of film-formation rate, it was confirmed to be 81 nm/minute.Then, by measurement of specific resistance of the film, it wasconfirmed to be 2.0×10⁻³≠·cm. Generated phases of the film wereidentified by X-ray diffraction measurement, and confirmed to beamorphous. In addition, extinction coefficient of a wavelength of 400 nmwas measured and found to be 0.02337.

The above evaluation results of a target and evaluation results offilm-formation are shown in Table 1.

Example 6

An oxide sintered body was prepared by a similar method as in Example 2,without changing the condition except that sintering temperature waschanged to 1250° C.

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure, constituted by indium and gallium, and the (Ga,In)₂O₃ phase. Intensity ratio of X-ray diffraction peak of the GaInO₃phase (111) represented by the above expression (1) was 28%. Density ofthe oxide sintered body was measured and found to be 6.33 g/cm³.Subsequently, constitution observation of the oxide sintered body wasperformed with SEM, and found that average particle diameter of theGaInO₃ phase was 2.4 μm.

The direct-current sputtering was performed till attaining of anintegrated charge power value of 12.8 KWh, by using this oxide sinteredbody as a sputtering target. Arcing did not generate during this period,and discharge was stable. After completion of sputtering, the targetsurface was observed and found no particular nodule generation. Then bychange of direct-current power to 200, 400, 500, 600 W (1.10 to 3.29W/cm²), sputtering was performed for 10 minutes under each power tomeasure arcing generation times. Under any power, arcing did notgenerate and average arcing generation times per 1 minute under eachdirect-current power were zero.

Subsequently, film-formation was performed by direct-current sputtering.It was confirmed that the composition of the obtained transparentconductive film was nearly the same as that of the target. Bymeasurement of film-formation rate, it was confirmed to be 83 nm/minute.Then, by measurement of specific resistance of the film, it wasconfirmed to be 9.1×10⁻⁴Ω·cm. Generated phases of the film wereidentified by X-ray diffraction measurement, and confirmed to beamorphous. In addition, extinction coefficient of a wavelength of 400 nmwas measured and found to be 0.02743.

The above evaluation results of a target and evaluation results offilm-formation are shown in Table 1.

Example 7

An oxide sintered body was prepared by a similar method as in Example 2,without changing the condition except that sintering temperature waschanged to 1450° C.

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure, constituted by indium and gallium, and the (Ga,In)₂O₃ phase. Intensity ratio of X-ray diffraction peak of the GaInO₃phase (111) represented by the above expression (1) was 31%. Density ofthe oxide sintered body was measured and found to be 6.88 g/cm³.Subsequently, constitution observation of the oxide sintered body wasperformed with SEM, and found that average particle diameter of theGaInO₃ phase was 3.3 μm.

The direct-current sputtering was performed till attaining of anintegrated charge power value of 12.8 KWh, by using this oxide sinteredbody as a sputtering target. Arcing did not generate during this period,and discharge was stable. After completion of sputtering, the targetsurface was observed and found no particular nodule generation. Then bychange of direct-current power to 200, 400, 500, 600 W (1.10 to 3.29W/cm²), sputtering was performed for 10 minutes under each power tomeasure arcing generation times. Under any power, arcing did notgenerate and average arcing generation times per 1 minute under eachdirect-current power were zero.

Subsequently, film-formation was performed by direct-current sputtering.It was confirmed that the composition of the obtained transparentconductive film was nearly the same as that of the target. Bymeasurement of film-formation rate, it was confirmed to be 87 nm/minute.Then, by measurement of specific resistance of the film, it wasconfirmed to be 8.0×10⁻⁴Ω·cm. Generated phases of the film wereidentified by X-ray diffraction measurement, and confirmed to beamorphous. In addition, extinction coefficient of a wavelength of 400 nmwas measured and found to be 0.02776.

The above evaluation results of a target and evaluation results offilm-formation are shown in Table 1.

Example 8

An oxide sintered body was prepared by a similar method as in Example 2,without changing the condition except that similar gallium atom numberratio as in Example 2, that is, the content of gallium as atom numberratio represented by Ga/(In+Ga+Sn), was dispensed to 20% by atom, andstill more, as the addition component, 6% by atom as atom number ratiorepresented by (Sn)/(In+Ga+Sn) of tin oxide powders with an averageparticle diameter of equal to or smaller than 1 μm was added.

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure constituted by indium and gallium, and the (Ga,In)₂O₃ phase. Intensity ratio of X-ray diffraction peak of the GaInO₃phase (111) represented by the above expression (3) was 51%. Density ofthe oxide sintered body was measured and found to be 6.71 g/cm³.Subsequently, constitution observation of the oxide sintered body wasperformed with SEM, and found that average particle diameter of theGaInO₃ phase was 2.9 μm.

The direct-current sputtering was performed till attaining of anintegrated charge power value of 12.8 KWh, by using this oxide sinteredbody as a sputtering target. Arcing did not generate during this period,and discharge was stable. After completion of sputtering, the targetsurface was observed and found no particular nodule generation. Then bychange of direct-current power to 200, 400, 500, 600 W (1.10 to 3.29W/cm²), sputtering was performed for 10 minutes under each power tomeasure arcing generation times. Under any power, arcing did notgenerate and average arcing generation times per 1 minute under eachdirect-current power were zero.

Subsequently, film-formation was performed by direct-current sputtering.It was confirmed that the composition of the obtained transparentconductive film was nearly the same as that of the target. Bymeasurement of film-formation rate, it was confirmed to be 89 nm/minute.Then, by measurement of specific resistance of the film, it wasconfirmed to be 9.1×10⁻⁴Ω·cm. Generated phases of the film wereidentified by X-ray diffraction measurement, and confirmed to beamorphous. In addition, extinction coefficient of a wavelength of 400 nmwas measured and found to be 0.03482.

The above evaluation results of a target and evaluation results offilm-formation are shown in Table 1. It should be noted that in the casewhere germanium oxide powders were used instead of tin oxide powders, oreven in the case where tin oxide powders and germanium oxide powderswere used at the same time, it was confirmed that nearly the sameresults are obtained.

Example 9

Film-formation was performed by changing the film-formation method to anion plating method, and by using a tablet made of an oxide sintered bodywith similar composition as in Example 2.

A preparation method for the oxide sintered body was nearly similarpreparation method as in the case of the sputtering target of Example 2,however, as described above, because density is required to be decreasedin the case of use as a tablet for ion plating, sintering temperaturewas set at 1100° C. The tablet was compacted in advance so as to attaindimension after sintering of a diameter of 30 mm, and a height of 40 mm.Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure constituted by indium and gallium, and the (Ga,In)₂O₃ phase. Intensity ratio of X-ray diffraction peak of the GaInO₃phase (111), represented by the above expression (1), was 27%. Densityof the oxide sintered body was measured and found to be 4.79 g/cm³.Subsequently, constitution observation of the oxide sintered body wasperformed with SEM, and found that average particle diameter of theGaInO₃ phase was 2.1 μm.

By using such an oxide sintered body as a target, discharge by using aplasma gun by an ion plating method was performed till the tablet becameunusable. As an ion plating apparatus, a reactive plasma vapordeposition apparatus, which is applicable to a high density plasmaassisted vapor deposition method (HDPE method), was used. Film-formationconditions were set as follows: a distance between an evaporation sourceand a substrate of 0.6 m, a discharge current of the plasma gun of 100A, an Ar flow rate of 30 sccm and an O₂ flow rate of 10 sccm. Problemsuch as splash was not raised, till the tablet became unusable.

Film-formation was performed after replacement of tablet. Composition ofthe obtained transparent conductive film was confirmed to be nearly thesame as that of the tablet. A film-formation rate of 122 nm/min wasobtained, and it was found that high rate film-formation equivalent toan ITO film was possible. Then, by measurement of specific resistance ofthe film, it was confirmed to be 6.5×10⁻⁴Ω·cm. Generated phases of thefilm were identified by X-ray diffraction measurement, and confirmed tobe amorphous. In addition, extinction coefficient of a wavelength of 400nm was measured and found to be 0.02722. The above evaluation results ofa target and evaluation results of film-formation are shown in Table 1.

Example 10

On a PES (polyethersulfone) film substrate with a thickness of 100 μm, asilicon oxynitride film with a thickness of 100 nm was formed inadvance, as a gas barrier film, and on said gas barrier film, atransparent conductive film composed of an oxide containing indium andgallium, with a thickness of 100 nm, was formed in the similar step asin Example 2, to prepare a transparent conductive substrate.

The obtained transparent conductive substrate was investigated, andconfirmed that the transparent conductive film formed similarly as inExample 2 was amorphous, having a specific resistance of 7.5×10⁻⁴ Ω·cm,and an average transmittance of a visible region of equal to or higherthan 85%, therefore good characteristics was obtained.

Example 11

An oxide sintered body was prepared by a similar method as in Example 8,without changing the condition except that the content of gallium ofExample 8, that is, atom number ratio represented by Ga/(In+Ga+Sn), waschanged to 2% by atom, along with tin was changed to 10% by atom as atomnumber ratio of represented by Sn/(In+Ga+Sn).

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure constituted by indium and gallium, and the (Ga,In)₂O₃ phase. Intensity ratio of X-ray diffraction peak of the GaInO₃phase (111) represented by the above expression (3) was 4%. Density ofthe oxide sintered body was measured and found to be 6.87 g/cm³.Subsequently, constitution observation of the oxide sintered body wasperformed with SEM, and found that average particle diameter of theGaInO₃ phase was 2.8 μm.

The direct-current sputtering was performed till attaining of anintegrated charge power value of 12.8 KWh, by using this oxide sinteredbody as a sputtering target. Arcing did not generate during this period,and discharge was stable. After completion of sputtering, the targetsurface was observed and found no particular nodule generation. Then bychange of direct-current power to 200, 400, 500, 600 W (1.10 to 3.29W/cm²), sputtering was performed for 10 minutes under each power tomeasure arcing generation times. Under any power, arcing did notgenerate and average arcing generation times per 1 minute under eachdirect-current power were zero.

Subsequently, film-formation was performed by direct-current sputtering.It was confirmed that the composition of the obtained transparentconductive film was nearly the same as that of the target. Bymeasurement of film-formation rate, it was confirmed to be 92 nm/minute.Then, by measurement of specific resistance of the film, it wasconfirmed to be 5.2×10⁻⁴ Ω·cm. Generated phases of the film wereidentified by X-ray diffraction measurement, and confirmed to beamorphous. In addition, extinction coefficient of a wavelength of 400 nmwas measured and found to be 0.03891.

The above evaluation results of a target and evaluation results offilm-formation are shown in Table 1. It should be noted that in the casewhere germanium oxide powders were used instead of tin oxide powders, oreven in the case where tin oxide powders and germanium oxide powderswere used at the same time, it was confirmed that nearly the sameresults are obtained.

Example 12

An oxide sintered body was prepared by a similar method as in Example 8,without changing the condition except that the content of gallium ofExample 8, that is, atom number ratio represented by Ga/(In+Ga+Sn), waschanged to 5% by atom, along with tin was changed to 10% by atom as atomnumber ratio of represented by Sn/(In+Ga+Sn).

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure constituted by indium and gallium, and the (Ga,In)₂O₃ phase. Intensity ratio of X-ray diffraction peak of the GaInO₃phase (111) represented by the above expression (3) was 7%. Density ofthe oxide sintered body was measured and found to be 6.90 g/cm³.Subsequently, constitution observation of the oxide sintered body wasperformed with SEM, and found that average particle diameter of theGaInO₃ phase was 2.7 μm.

The direct-current sputtering was performed till attaining of anintegrated charge power value of 12.8 KWh, by using this oxide sinteredbody as a sputtering target. Arcing did not generate during this period,and discharge was stable. After completion of sputtering, the targetsurface was observed and found no particular nodule generation. Then bychange of direct-current power to 200, 400, 500, 600 W (1.10 to 3.29W/cm²), sputtering was performed for 10 minutes under each power tomeasure arcing generation times. Under any power, arcing did notgenerate and average arcing generation times per 1 minute under eachdirect-current power were zero.

Subsequently, film-formation was performed by direct-current sputtering.It was confirmed that the composition of the obtained transparentconductive film was nearly the same as that of the target. Bymeasurement of film-formation rate, it was confirmed to be 92 nm/minute.Then, by measurement of specific resistance of the film, it wasconfirmed to be 5.0×10⁻⁴ Ω·cm. Generated phases of the film wereidentified by X-ray diffraction measurement, and confirmed to beamorphous. In addition, extinction coefficient of a wavelength of 400 nmwas measured and found to be 0.03711.

The above evaluation results of a target and evaluation results offilm-formation are shown in Table 1.

Example 13

An oxide sintered body was prepared by a similar method as in Example 8,without changing the condition except that the content of gallium ofExample 8, that is, atom number ratio represented by Ga/(In+Ga+Sn), waschanged to 10% by atom, along with tin was changed to 10% by atom asatom number ratio of represented by Sn/(In+Ga+Sn).

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure constituted by indium and gallium, and the (Ga,In)₂O₃ phase. Intensity ratio of X-ray diffraction peak of the GaInO₃phase (111) represented by the above expression (3) was 48%. Density ofthe oxide sintered body was measured and found to be 6.99 g/cm³.Subsequently, constitution observation of the oxide sintered body wasperformed with SEM, and found that average particle diameter of theGaInO₃ phase was 2.5 μm.

The direct-current sputtering was performed till attaining of anintegrated charge power value of 12.8 KWh, by using this oxide sinteredbody as a sputtering target. Arcing did not generate during this period,and discharge was stable. After completion of sputtering, the targetsurface was observed and found no particular nodule generation. Then bychange of direct-current power to 200, 400, 500, 600 W (1.10 to 3.29W/cm²), sputtering was performed for 10 minutes under each power tomeasure arcing generation times. Under any power, arcing did notgenerate and average arcing generation times per 1 minute under eachdirect-current power were zero.

Subsequently, film-formation was performed by direct-current sputtering.It was confirmed that the composition of the obtained transparentconductive film was nearly the same as that of the target. Bymeasurement of film-formation rate, it was confirmed to be 90 nm/minute.Then, by measurement of specific resistance of the film, it wasconfirmed to be 6.4×10⁻⁴Ω·cm. Generated phases of the film wereidentified by X-ray diffraction measurement, and confirmed to beamorphous. In addition, extinction coefficient of a wavelength of 400 nmwas measured and found to be 0.03663.

The above evaluation results of a target and evaluation results offilm-formation are shown in Table 1.

Example 14

An oxide sintered body was prepared by a similar method as in Example 8,without changing the condition except that the content of gallium ofExample 8, that is, atom number ratio represented by Ga/(In+Ga+Sn), waschanged to 15% by atom, along with tin was changed to 2% by atom as atomnumber ratio of represented by Sn/(In+Ga+Sn).

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure constituted by indium and gallium, and the (Ga,In)₂O₃ phase. In addition, presence of a Ga₂In₆Sn₂O₁₆ phase was alsoconfirmed partially, although very weak. Intensity ratio of X-raydiffraction peak of the GaInO₃ phase (111) represented by the aboveexpression (3) was 32%. Density of the oxide sintered body was measuredand found to be 7.01 g/cm³. Subsequently, constitution observation ofthe oxide sintered body was performed with SEM, and found that averageparticle diameter of the GaInO₃ phase was 2.6 μm. In addition, it wasconfirmed that particle diameter of the crystal of the Ga₂In₆Sn₂O₁₆phase was equal to or smaller than 3 μm.

The direct-current sputtering was performed till attaining of anintegrated charge power value of 12.8 KWh, by using this oxide sinteredbody as a sputtering target. Arcing did not generate during this period,and discharge was stable. After completion of sputtering, the targetsurface was observed and found no particular nodule generation. Then bychange of direct-current power to 200, 400, 500, 600 W (1.10 to 3.29W/cm²), sputtering was performed for 10 minutes under each power tomeasure arcing generation times. Under any power, arcing did notgenerate and average arcing generation times per 1 minute under eachdirect-current power were zero.

Subsequently, film-formation was performed by direct-current sputtering.It was confirmed that the composition of the obtained transparentconductive film was nearly the same as that of the target. Bymeasurement of film-formation rate, it was confirmed to be 89 nm/minute.Then, by measurement of specific resistance of the film, it wasconfirmed to be 6.2×10⁻⁴ Ω·cm. Generated phases of the film wereidentified by X-ray diffraction measurement, and confirmed to beamorphous. In addition, extinction coefficient of a wavelength of 400 nmwas measured and found to be 0.03402.

The above evaluation results of a target and evaluation results offilm-formation are shown in Table 1.

Example 15

An oxide sintered body was prepared by a similar method as in Example 8,without changing the condition except that the content of gallium ofExample 8, that is, atom number ratio represented by Ga/(In+Ga+Sn), waschanged to 30% by atom, along with tin was changed to 3% by atom as atomnumber ratio of represented by Sn/(In+Ga+Sn).

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure constituted by indium and gallium, and the (Ga,In)₂O₃ phase. Intensity ratio of X-ray diffraction peak of the GaInO₃phase (111) represented by the above expression (3) was 84%. Density ofthe oxide sintered body was measured and found to be 6.71 g/cm³.Subsequently, constitution observation of the oxide sintered body wasperformed with SEM, and found that average particle diameter of theGaInO₃ phase was 2.8 μm.

The direct-current sputtering was performed till attaining of anintegrated charge power value of 12.8 KWh, by using this oxide sinteredbody as a sputtering target. Arcing did not generate during this period,and discharge was stable. After completion of sputtering, the targetsurface was observed and found no particular nodule generation. Then bychange of direct-current power to 200, 400, 500, 600 W (1.10 to 3.29W/cm²), sputtering was performed for 10 minutes under each power tomeasure arcing generation times. Under any power, arcing did notgenerate and average arcing generation times per 1 minute under eachdirect-current power were zero.

Subsequently, film-formation was performed by direct-current sputtering.It was confirmed that the composition of the obtained transparentconductive film was nearly the same as that of the target. Bymeasurement of film-formation rate, it was confirmed to be 85 nm/minute.Then, by measurement of specific resistance of the film, it wasconfirmed to be 1.8×10⁻³ Ω·cm. Generated phases of the film wereidentified by X-ray diffraction measurement, and confirmed to beamorphous. In addition, extinction coefficient of a wavelength of 400 nmwas measured and found to be 0.03213.

The above evaluation results of a target and evaluation results offilm-formation are shown in Table 1.

Comparative Example 1

An oxide sintered body was prepared by a similar method as in Example 1,without changing the condition except that the content of gallium asatom number ratio represented by Ga/(In+Ga) was changed to 3% by atom.

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Density of the oxide sintered body was measured and found to be 7.06g/cm³. Next, phase identification of the oxide sintered body wasperformed by X-ray diffraction measurement, and it was confirmed to beconstituted only by the In₂O₃ phase with a bixbyite-type structure. Thatis, it was judged that the oxide sintered body, constituted by the In₂O₃phase with a bixbyite-type structure having substantially a solidsolution of gallium, the GaInO₃ phase of a β-Ga₂O₃-type structureconstituted by indium and gallium, and/or the (Ga, In)₂O₃ phase, of thepresent invention, was not obtained in this composition. Therefore,further target evaluation was not performed, and only film-formation bydirect-current sputtering was performed.

It was confirmed that the composition of the obtained transparentconductive film by direct-current sputtering was nearly the same as thatof the target. By measurement of film-formation rate, it was confirmedto be 86 nm/minute. Then, by measurement of specific resistance of thefilm, it was confirmed to be 8.3×10⁻⁴ Ω·cm. Generated phases of the filmwere identified by X-ray diffraction measurement, and confirmed to beamorphous. In addition, extinction coefficient of a wavelength of 400 nmwas measured and found to be 0.04188. The above evaluation results of atarget and evaluation results of film-formation are shown in Table 1.

Comparative Example 2

An oxide sintered body was prepared by a similar method as in Example 1,without changing the condition except that the content of gallium asatom number ratio represented by Ga/(In+Ga) was changed to 40% by atom.

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure constituted by indium and gallium, and the (Ga,In)₂O₃ phase. Then as Example 2, an X-ray diffraction chart of the oxidesintered body is shown in FIG. 2. Intensity ratio of X-ray diffractionpeak of the GaInO₃ phase (111) represented by the above expression (1)was 74%. Density of the oxide sintered body was measured and found to be6.54 g/cm³. Subsequently, constitution observation of the oxide sinteredbody was performed with SEM, and found that average particle diameter ofthe GaInO₃ phase was 4.2 μm.

The direct-current sputtering was performed till attaining of anintegrated charge power value of 12.8 KWh, by using this oxide sinteredbody as a sputtering target. Arcing did not generate during this period,and discharge was stable. After completion of sputtering, the targetsurface was observed and found no particular nodule generation. Then bychange of direct-current power to 200, 400, 500, 600 W (1.10 to 3.29W/cm²), sputtering was performed for 10 minutes under each power tomeasure arcing generation times. Under any power, arcing did notgenerate and average arcing generation times per 1 minute under eachdirect-current power were zero.

Subsequently, film-formation was performed by direct-current sputtering.It was confirmed that the composition of the obtained transparentconductive film was nearly the same as that of the target. Bymeasurement of film-formation rate, it was confirmed to be 62 nm/minute.Then, by measurement of specific resistance of the film, it wasconfirmed to be 3.5×10⁻³ Ω·cm. Generated phases of the film wereidentified by X-ray diffraction measurement, and confirmed to beamorphous. In addition, extinction coefficient of a wavelength of 400 nmwas measured and found to be 0.01811.

The above evaluation results of a target and evaluation results offilm-formation are shown in Table 1.

Comparative Example 3

An oxide sintered body was prepared by a similar method as in Example 2,without changing the condition except that indium oxide powders andgallium oxide powders with average particle diameter of about 3 μm wereused.

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure constituted by indium and gallium, and the (Ga,In)₂O₃ phase. Intensity ratio of X-ray diffraction peak of the GaInO₃phase (111) represented by the above expression (1) was 42%. Density ofthe oxide sintered body was measured and found to be 6.23 g/cm³.Subsequently, constitution observation of the oxide sintered body wasperformed with SEM, and found that average particle diameter of theGaInO₃ phase was 5.8 μm.

The direct-current sputtering was performed till attaining of anintegrated charge power value of 12.8 KWh, by using this oxide sinteredbody as a sputtering target. For certain period after starting thesputtering, arcing did not generate, however, at the time reaching nearthe above integration time, arcing gradually generated. Target surfacewas observed after reaching the above integration time, and generationof many nodules were confirmed. Then by change of direct-current powerto 200, 400, 500, 600 W (1.10 to 3.29 W/cm²), sputtering was performedfor 10 minutes under each power to measure arcing generation times. FIG.3 shows arcing generation times per 1 minute under each direct-currentpower, along with Example 2. From FIG. 3, it is clear that generation ofarcing becomes frequent with increase in direct-current power.

Film-formation was performed by direct-current sputtering by using thisoxide sintered body as a sputtering target. Arcing generated frequentlyduring film-formation. It was confirmed that the composition of theobtained transparent conductive film was nearly the same as that of thetarget. By measurement of film-formation rate, it was confirmed to be 71nm/minute. Then, generated phases of the film were identified by X-raydiffraction measurement, and confirmed to be amorphous. By measurementof specific resistance of the film, it was confirmed to be 4.1×10⁻³Ω·cm. In addition, extinction coefficient of a wavelength of 400 nm wasmeasured and found to be 0.03323. The above evaluation results of atarget and evaluation results of film-formation are shown in Table 1.

Comparative Example 4

An oxide sintered body was prepared by a similar method as in Example 2,without changing the condition except that sintering temperature waschanged to 1000° C.

Composition analysis of the obtained oxide sintered body was performedby an ICP emission spectrometry, and it was confirmed to be nearly thesame as charging composition in formulation of raw material powders.Next, phase identification of the oxide sintered body was performed byX-ray diffraction measurement, and it was confirmed to be constituted bythe In₂O₃ phase with a bixbyite-type structure, the GaInO₃ phase with aβ-Ga₂O₃-type structure constituted by indium and gallium, and the (Ga,In)₂O₃ phase. Intensity ratio of X-ray diffraction peak of the GaInO₃phase (111) represented by the above expression (1) was 26%. Density ofthe oxide sintered body was measured and found to be 5.73 g/cm³.Subsequently, constitution observation of the oxide sintered body wasperformed with SEM, and found that average particle diameter of theGaInO₃ phase was 2.1 μm.

Direct-current sputtering was performed by using this oxide sinteredbody as a sputtering target. After starting the sputtering, arcinggenerated at the early stage, and continuation of the sputtering becameimpossible for a long time when an integration charge power valuereached 12.8 kWh. Target surface was observed and confirmed generationof cracks. Therefore, measurement of arcing generation times wasabandoned, and direct-current sputtering under low power condition wastried. The sputtering was possible till a charge power of about 30 W,however, arcing became generating when the power was over 50 W.Therefore, it was judged that practical film-formation was impossible.

The above evaluation results of a target and evaluation results offilm-formation are shown in Table 1.

Comparative Example 5

Film-formation was performed by direct-current sputtering by using acommercially available ITO target (In₂O₃-10% by weight SnO₂,manufactured by Sumitomo Metal Mining Co., Ltd.). Density of the ITOtarget was measured and found to be 7.11 g/cm³. Composition of theobtained transparent conductive film was confirmed to be nearly the sameas the target. By measurement of film-formation rate, it was confirmedto be 92 nm/minute. Then, generated phases of the film were identifiedby X-ray diffraction measurement, and confirmed to be amorphous. Bymeasurement of specific resistance of the film, it was confirmed to be4.9×10⁻⁴ Ω·cm. In addition, extinction coefficient of a wavelength of400 nm was measured and found to be 0.04308. The above evaluationresults of a target and evaluation results of film-formation are shownin Table 1.

TABLE 1 Target evaluation GaInO₃ Ga Sn phase GaInO₃ (111) atom atomcrystal or (−111) Nodule Arcing Sintering ratio ratio grain peakgeneration generation temperature [% by [% by diameter intensity (◯Yes,(◯Yes, Density [° C.] atom] atom] [μm] ratio XNo) XNo) [g/cm3] Example 11400 10 — 2.9  8 ◯ ◯ 6.97 Example 2 1400 20 — 2.6 30 ◯ ◯ 6.84 Example 31400 25 — 2.5 39 ◯ ◯ 6.77 Example 4 1400 30 — 2.8 49 ◯ ◯ 6.70 Example 51400 34 — 4.1 58 ◯ ◯ 6.63 Example 6 1250 20 — 2.4 28 ◯ ◯ 6.33 Example 71450 20 — 3.3 31 ◯ ◯ 6.88 Example 8 1400 20  6 2.9 51 ◯ ◯ 6.71 Example 91100 20 — 2.1 27 ◯ ◯ 4.79 Example 11 1400 2 10 2.8  4 ◯ ◯ 6.87 Example12 1400 5 10 2.7  7 ◯ ◯ 6.90 Example 13 1400 10 10 2.5 48 ◯ ◯ 6.99Example 14 1400 15  2 2.6 32 ◯ ◯ 7.01 Example 15 1400 30  3 2.8 84 ◯ ◯6.71 Com. Ex. 1 1400 3 — no — — — 7.06 generation of GaInO₃ Com. Ex. 21400 40 — 4.2 74 ◯ ◯ 6.54 Com. Ex. 3 1400 20 — 5.8 42 X X 6.23 Com. Ex.4 1000 20 — 2.1 26 ◯ X 5.73 Com. Ex. 5 ITO (In₂O₃—10 wt % SnO₂) — — 7.11Film-formation evaluation Film- Film- formation Specific formation rateresistance Extinction method [nm/min] [Ωcm] coefficient CrystallinityExample 1 sputtering 93 4.9 × 10⁻⁴ 0.03198 amorphous Example 2sputtering 86 7.8 × 10⁻⁴ 0.02769 amorphous Example 3 sputtering 86 8.8 ×10⁻⁴ 0.02591 amorphous Example 4 sputtering 84 1.4 × 10⁻³ 0.02361amorphous Example 5 sputtering 81 2.0 × 10⁻³ 0.02337 amorphous Example 6sputtering 83 9.1 × 10⁻⁴ 0.02743 amorphous Example 7 sputtering 87 8.0 ×10⁻⁴ 0.02776 amorphous Example 8 sputtering 89 9.1 × 10⁻⁴ 0.03482amorphous Example 9 ion plating 122  6.5 × 10⁻⁴ 0.02722 amorphousExample 11 sputtering 92 5.2 × 10⁻⁴ 0.03891 amorphous Example 12sputtering 92 5.0 × 10⁻⁴ 0.03711 amorphous Example 13 sputtering 90 6.4× 10⁻⁴ 0.03663 amorphous Example 14 sputtering 89 6.2 × 10⁻⁴ 0.03402amorphous Example 15 sputtering 85 1.8 × 10⁻³ 0.03213 amorphous Com. Ex.1 sputtering 86 8.3 × 10⁻⁴ 0.04188 amorphous Com. Ex. 2 sputtering 623.5 × 10⁻³ 0.01811 amorphous Com. Ex. 3 sputtering 71 4.1 × 10⁻³ 0.03323amorphous Com. Ex. 4 sputtering — — — — Com. Ex. 5 sputtering 92 4.9 ×10⁻⁴ 0.04308 amorphous[Evaluation]

From Examples 1 to 7, it was confirmed that the oxide sintered bodysintered at a sintering temperature of from 1250 to 1400° C. by usingthe indium oxide powders and the gallium oxide powders with averageparticle diameter adjusted to equal to or smaller than 1 μm, and havingcontent of gallium as atom number ratio of Ga/(In+Ga) in a range ofequal to or higher than 10% by atom and below 35% by atom, wasconstituted by the In₂O₃ phase with a bixbyite-type structure having asolid solution of gallium, and the GaInO₃ phase of a β-Ga₂O₃-typestructure constituted by indium and gallium, or the In₂O₃ phase with abixbyite-type structure having a solid solution of gallium, and theGaInO₃ phase of a β-Ga₂O₃-type structure constituted by indium andgallium and the (Ga, In)₂O₃ phase). In addition, it was confirmed thatintensity ratio of X-ray diffraction peaks of In₂O₃ phase (400) andGaInO₃ phase (111) is from 8% to 58%, and finely dispersed constitution,wherein the crystal grains composed of the GaInO₃ phase, or the GaInO₃phase and the (Ga, In)₂O₃ phase have an average particle diameter ofequal to or smaller than 5 μm, is obtained.

In particular, Examples 1 to 4 and 6 provided a constitution, whereinthe crystal grains composed of the GaInO₃ phase, or the GaInO₃ phase andthe (Ga, In)₂O₃ phase are finely dispersed in an average particlediameter of equal to or smaller than 3 μm. In addition, densities of thesintered bodies were equal to or higher than 6.3 g/cm³, all exhibitedhigh densities. Direct-current sputtering was performed by using theseoxide sintered bodies as sputtering targets, and it was clarified thatthere was no generation of nodules starting from the digging-residues ofsputtering, even after continuous sputtering over a long time, and therewas no arching generation even by changing the direct-current power in arange of from 200 to 600 W (1.10 to 3.29 W/cm²).

Film-formation rates in Examples 1 to 7 were from 81 to 93 nm/min, itwas by no means inferior to a film-formation rate of ITO in ComparativeExample 5 of 92 nm/min. Specific resistances of the obtained transparentconductive films are good, such as equal to or lower than 2×10⁻³Ω·cm,and in particular, in Examples 1 to 3, 6 and 7, in the case where acontent of gallium is set to be from 10% to 25% by atom as atom numberratio of Ga/(In+Ga), still more lower specific resistances of 1×10⁻⁴Ω·cm level were obtained. In addition, extinction coefficient of thefilms at a wavelength of 400 nm showed from about 0.02 to 0.03, allshowed equal to or lower than 0.04. Since the ITO film has extinctioncoefficient of over 0.04, it was confirmed that films of Examples 1 to 7have low absorption of blue light.

Different point of Comparative Examples 1 and 2 compared with Examples 1to 7 is that content of gallium as atom number ratio of Ga/(In+Ga) isnot within a range of is equal to or higher than 10% by atom and below35% by atom. In the case of low gallium content, crystal grains composedof the GaInO₃ phase, or the GaInO₃ phase and the (Ga, In)₂O₃ phase arenot formed, and extinction coefficient at a wavelength of 400 nm becomesover 0.04. On the other hand, in the case of high gallium content,film-formation rate decreases significantly and also specific resistanceof the film increases inevitably. Therefore it is clear that compositionrange providing good balance of the above characteristics is thatcontent of gallium as atom number ratio of Ga/(In+Ga) is equal to orhigher than 10% by atom and below 35% by atom.

Different point of Comparative Example 3 compared with Examples 1 to 7is that relatively coarse indium oxide powders and gallium oxide powderswith an average particle diameter of 3 μm were used, which brought aboutthat the crystal grains composed of the GaInO₃ phase, or the GaInO₃phase and the (Ga, In)₂O₃ phase dispersed in the oxide sintered body hadan average particle diameter of over 5 μm. Direct-current sputtering wasperformed by using these oxide sintered bodies having suchconstitutions, as sputtering targets, and it was confirmed that nodulesgenerated and arcing generated frequently after continuous sputteringfor a long time. That is, it was clarified that, as in Examples 1 to 7,such constitutions of the oxide sintered body wherein the crystal grainscomposed of the GaInO₃ phase, or the GaInO₃ phase and the (Ga, In)₂O₃phase are finely dispersed therein so as to have an average particlediameter of equal to or smaller than 5 μm, by using indium oxide powdersand gallium oxide powders, with average particle diameter adjusted toequal to or smaller than 1 μm, are effective in suppression of nodulegeneration and arcing generation.

In addition, in Comparative Example 4, because sintering temperature wasas low as 1000° C. compared with Examples 1 to 7, sintering did notprogress and although the average particle diameter of the crystalgrains composed of the GaInO₃ phase, or the GaInO₃ phase and the (Ga,In)₂O₃ phase was equal to or smaller than 5 μm, density of the sinteredbody did not reach 6.3 g/cm². In direct-current sputtering, a crackgenerated at the sputtering target and sputtering was limited only undera low power condition of about 30 W, and film-formation wassubstantially impossible. That is, it was clarified that for sufficientprogress of sintering, a sintering temperature of 1000° C. isinsufficient, and from 1250 to 1450° C. is suitable.

By Examples 8, 11 to 15, it was confirmed that the oxide sintered bodiesadded with tin, germanium, or both, or also the transparent conductivefilms exhibit good characteristics similarly as the oxide sinteredbodies containing gallium and indium, or the transparent conductivefilms of Examples 1 to 7. In particular, by Examples 11 and 12, it wasconfirmed that in the case where tin or germanium, or both are added,even when gallium is in a composition range of lower addition quantity,an oxide sintered body composed of the In₂O₃ phase with a bixbyite-typestructure having a solid solution of gallium and tin as a mother phasecan be obtained, which is finely dispersed with the GaInO₃ phase of aβ-Ga₂O₃-type structure constituted by indium, gallium and tin having anaverage particle diameter of equal to or smaller than 5 μm, or theGaInO₃ phase and the (Ga, In)₂O₃ phase of a β-Ga₂O₃-type structure,constituted by indium, gallium and tin, having an average particlediameter of equal to or smaller than 5 μm, similar to those in Examples1 to 7, and still more those constitutions are effective in suppressionof nodule generation and arcing generation.

In addition, by Example 9, it was clarified that, even in the case of anion plating method, an oxide sintered body or a transparent conductivefilm exhibiting good characteristics can be obtained similarly as inExamples 1 to 8. Still more, by Example 10, it is found that by usingthe oxide sintered body of the present invention, a transparentconductive film exhibiting good characteristics, similarly as inExamples 1 to 9, can also be formed on a resin substrate with amoisture-proof film, if necessary, without limiting to a glasssubstrate.

What is claimed is:
 1. An oxide sintered body comprising indium andgallium as an oxide, characterized in that an In₂O₃ phase with abixbyite-type structure forms a major crystal phase, and GaInO₃ phase isfinely dispersed as a crystal grain having an average particle diameterof equal to or smaller than 4.1 μm, and a content of gallium is equal toor higher than 25% by atom and below 34% by atom as atom number ratio ofGa/(In+Ga).
 2. The oxide sintered body according to claim 1,characterized in that intensity ratio of X-ray diffraction peaks definedby the following expression, is from 8% to 58%:I[GaInO₃ phase (111)]/{I[In₂O₃ phase (400)]+I[GaInO₃ phase(111)]}×100[%] (wherein, I[In₂O₃ phase (400)] represents (400) peakintensity of the In₂O₃ phase with a bixbyite-type structure, andI[GaInO₃ phase (111)] represents (111) peak intensity of a compositeoxide of β-GaInO₃ phase with a β-Ga₂O₃-type structure).
 3. The oxidesintered body according to claim 1, characterized in that other than theindium and the gallium, further one or more kinds of additive componentsselected from tin or germanium are contained, and the content of thegallium is from 2 to 30% by atom as atom number ratio ofGa/(In+Ga+Sn+Ge), and the content of the additive components is from 1to 11% by atom as atom number ratio of (Sn+Ge)/(In+Ga+Sn+Ge).
 4. Theoxide sintered body according to claim 3, characterized in that thecontent of gallium is from 2 to 20% by atom as atom number ratio ofGa/(In+Ga+Sn+Ge), and the content of one or more kinds selected from tinor germanium is from 2 to 10% by atom as atom number ratio of(Sn+Ge)/(In+Ga+Sn+Ge).
 5. The oxide sintered body according to claim 3,characterized in that intensity ratio of X-ray diffraction peaks definedby the following expression, is from 4% to 84%:I[GaInO₃ phase (−111)]/{I[In₂O₃ phase (400)]+I[GaInO₃ phase(−111)]}×100[%] (wherein, I[In₂O₃ phase (400)] represents (400) peakintensity of the In₂O₃ phase with a bixbyite-type structure, andI[GaInO₃ phase (−111)] represents (−111) peak intensity of a compositeoxide of β-GaInO₃ phase with a β-Ga₂O₃-type structure).
 6. A productionmethod for the oxide sintered body according to claim 1, by mixing theraw material powders comprising indium oxide powders and gallium oxidepowders, or by adding the tin oxide powders and/or germanium oxidepowders into this raw material powders, and mixing the mixture, and thenby compacting the mixed powders and sintering the compact by a normalpressure firing method, or by compacting and sintering the mixed powdersby a hot press method, characterized by obtaining of the oxide sinteredbody, where an In₂O₃ phase with a bixbyite-type structure forms a majorcrystal phase, and a GaInO₃ phase is finely dispersed therein, as acrystal grain having an average particle diameter of equal to or smallerthan 4.1 μm, by adjustment of average particle diameter of the rawmaterial powders to equal to or smaller than 1μm.
 7. The productionmethod for the oxide sintered body according to claim 6, characterizedin that the compact is sintered at 1250 to 1450° C. for 10 to 30 hoursin atmosphere of oxygen presence, by adoption of the normal pressurefiring method.
 8. The production method for the oxide sintered bodyaccording to claim 6, characterized in that the compact is sintered at1000 to 1200° C. for 10 to 30 hours in atmosphere of oxygen presence, byadoption of the normal pressure firing method.
 9. The production methodfor the oxide sintered body according to claim 6, characterized in thatthe mixed powders are compacted and sintered at 700 to 950° C. for 1 to10hours under a pressure of 2.45 to 29.40 MPa in inert gas atmosphere orin vacuum, by adoption of a hot press method.
 10. A target obtained byprocessing the oxide sintered body according to claim
 1. 11. A target,characterized by obtaining by processing the oxide sintered bodyproduced by the method according to claim 7, wherein density of theoxide sintered body is equal to or higher than 6.3 g/cm³, and being usedin formation of a transparent conductive film by a sputtering method.12. A target, characterized by obtaining by processing the oxidesintered body produced by the method according to claim 8, whereindensity of the oxide sintered body is from 3.4 to 5.5 g/cm³, and beingused in formation of a transparent conductive film by an ion platingmethod.
 13. An amorphous transparent conductive film obtained by usingthe target according to claim 10, and by forming on a substrate, by asputtering method or an ion plating method.
 14. The transparentconductive film according to claim 13, characterized in that the contentof gallium in the film is from 2 to 30% by atom as atom number ratio ofGa/(In+Ga+Sn+Ge), and the content of one or more kinds selected from tinor germanium is from 1to 11% by atom as atom number ratio of(Sn+Ge)/(In+Ga+Sn+Ge).
 15. The transparent conductive film according toclaim 13, characterized in that the sputtering is performed undercondition that arcing does not generate, even by charging adirect-current power density of 1.10 to 3.29 W/cm².
 16. The transparentconductive film according to claim 13, characterized in that arithmeticaverage height Ra is equal to or lower than 1.0 nm.
 17. The transparentconductive film according to claim 13, characterized in that extinctioncoefficient at a wavelength of 400 nm is equal to or smaller than 0.04.18. The transparent conductive film according to claim 13, characterizedin that specific resistance is equal to or lower than 2×10⁻³Ω·cm.
 19. Atransparent conductive substrate comprising by forming the transparentconductive film according to claim 13, onto one surface or both surfacesof the transparent conductive substrate.
 20. The transparent conductivesubstrate according to claim 19, characterized in that a transparentsubstrate is any of a glass plate, a quartz plate, a resin plate or aresin film.
 21. The transparent conductive substrate according to claim20, characterized in that the resin plate or the resin film is a singlebody made of polyethylene terephthalate, polyethersulfone, polyarylateor polycarbonate as a material, or a laminated structure body wheresurface thereof is covered with an acryl-based organic substance. 22.The transparent conductive substrate according to claim 20,characterized in that the resin plate or the resin film is covered witha gas barrier film at one surface or both surfaces thereof, or is alaminated body inserted with a gas barrier film at the intermediate partthereof.
 23. The transparent conductive substrate according to claim 22,characterized in that the above gas barrier film is one or more kindsselected from a silicon oxide film, a silicon oxynitride film, amagnesium aluminate film, a tin oxide-based film, or a diamond-likecarbon film.